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COLD  STORAGE,  HEATING 

AND  VENTILATING  ON 

BOARD  SHIP 


BY 


SYDNEY   F.   WALKER,   R.N. 

N.  I.  E.  E.,     M.  I.  M.  E.,     N.  C.  S.  I.  A.,     M.  INST.  M.  E. 


ILLUSTRA TED 


>* >  .j „  j°«  *„  » 


NEW    YORK 
D.  VAN    NOSTRAND    COMPANY 

23  Murray  and  27  Warren  Streets 
191  i 


Reprinted  from 
INTERNATIONAL  MARINE  ENGINEERING 


Copyright,   1 911, 

BY 

D.  VAN  NOSTRAND  COMPANY 


<  <  t     c 


<\  :  :  •  :  •. :  •    ■  «;  : 


THE    SCIENTIFIC   PRESS 

ROBERT    DRUMMOND    AND    COMPANY 

NEW    YORK 


PREFACE 


Every  problem  in  engineering  requires  a  special  solution 
when  applied  to  marine  work.  The  limitations  of  weight  and 
space  on  board  ship,  and  the  absolute  necessity  for  reliability 
and  economy  introduce  factors  which  can  be  disregarded 
in  many  similar  problems  in  connection  with  machinery  in- 
stalled on  shore.  Refrigerating  machines  and  heating  and 
ventilating  apparatus  are  no  exceptions  to  this  rule,  and  in 
this  book  an  attempt  has  been  made  to  treat  the  problem 
of  cold  storage  and  heating  and  ventilating  exactly  as  it 
presents  itself  to  a  naval  architect  and  marine  engineer.  The 
reader  will  find  the  treatment  not  merely  descriptive,  but 
thoroughly  practical  from  an  engineering  standpoint.  About 
one- third  of  that  part  of  the  book  which  deals  with  cold  storage 
is  devoted  to  a  discussion  of  "faults"  which  may  occur  in  the 
apparatus.  Directions  are  given  for  hunting  down  various 
troubles  and  repairing  them,  and,  what  is  more  important, 
explicit  instructions  are  given  for  operating  various  types  of 
plants,  so  as  to  avoid  breakdowns.  Comparatively  little  has 
hitherto  been  published  on  the  subjects  covered  by  this  book. 
Therefore,  exceptional  pains  have  been  taken  to  make  the 
present  treatment  exhaustive  and  thoroughly  up  to  date. 


216664 


CONTENTS 


PAGE 

Cold  Storage  on  Board  Ship i 

Introduction.  The  Cold  Storage  Problem.  Methods 
of  Cooling  the  Cold  Chambers.  Direct  Expansion. 
Cooling  the  Chamber  by  Cooling  the  Air.  Cooling  the 
Air  Entering  Cold  Chambers.  Methods  of  Cooling  the 
Air.  Cooling  the  Air  by  Compression  and  Expansion. 
Leading  the  Cooled  Air  into  the  Cold  Chambers.  The 
Doors  of  Cold  Chambers.  How  the  Low  Temperature 
of  the  Brine  or  Refrigerant  is  Produced.  The  Condenser. 
Lubrication  and  Stuffing  Boxes  of  Compressors.  Absorp- 
tion Machines.  Circulating  Pumps.  How  Refrigerating 
Apparatus  is  Measured.  The  Power  Required  for  Re- 
frigerating Apparatus.  Cooling  Water.  Forms  of 
Apparatus  for  Use  on  Board  Ship.  Other  Applications 
of  Refrigeration  on  Board  Ship.  Cooling  Magazines  and 
Officers'  and  Men's  Quarters.  Faults.  Watch  the 
Gages.  If  the  Delivery  Pipe  Becomes  Hot.  If  the 
Delivery  Pipe  Becomes  Cold.  What  Follows  from 
a  Hot  Compressor.  Getting  Oil  and  Foreign  Bodies  Out 
of  the  System.  To  Test  Ammonia  for  Purity.  Faults 
in  Evaporating  Coils.  Troubles  with  Compressor  Valves. 
Testing  the  Gages.  Faults  in  the  Brine  Circulating 
System.  Preparing  the  Brine  Solution.  Faults  in  Air 
Cooled  Plants.  Faults  in  Cold  Chambers.  Receiving 
Meat  and  Produce.  Thawing  Out.  Handling  Meat  and 
Produce  when  Loading  and  Discharging.  Faults  in  an 
Absorption  Plant, 

V 


VI  CONTENTS 

PAGE 

Heating 124 

Special  Requirements  on  Board  Ship.  Difficulties 
Peculiar  to  Ship  Work.  Methods  of  Heating  Available. 
The  System  of  Heating  by  Hot  Water.  Difficulties  in 
Connection  with  Heating  by  Water.  The  Air  Trouble. 
Arrangement  of  Hot  Water  Heating  Systems.  Forms 
of  Heating  Apparatus  with  Hot  Water.  Heating  by 
Steam.  A  Combined  Air  and  Steam  Radiator.  Special 
Air  Heating  Stoves.  Heating  the  Air  by  Means  of 
Steam,  Hot  Water,  and  Electric  Radiators.  Air  Heating 
Apparatus  Pure  and  Simple.  The  Thermotank  System. 
Application  of  the  Thermotank  to  S.  S.  Lusitania.  Heat- 
ing by  Electricity.  Glow  Lamp  Radiators.  Non-Lumi- 
nous Heating  Apparatus.  Spiral  Coil  Heaters.  Low 
Temperature  Air  Heater,  Tubular  Type.  Regulating  the 
Heat  Delivered  by  Electric  Heating  Apparatus.  Quan- 
tity of  Heat  Liberated  in  Electrical  Heating  Apparatus. 

Ventilation 220 

Ventilation  by  Heating  and  Cooling.  Ventilation  of 
Lavatories  and  Cattle  Spaces.  Fans  Used  in  Ventilating. 
Size  of  Fans  Required.  Power  Required  by  the  Fan. 
Testing  the  Air  Current.  Estimating  the  Heat  to  be 
Required.  Heat  Passing  Out  through  the  Ship's  Side, 
Bulkheads,  etc.  Heating  by  Electricity  of  a  Large 
Passenger  Vessel.  Apparatus  Estimated  to  be  Required 
for  Heating  the  Different  Saloons,  State  Cabins,  etc. 
Cost  of  Furnishing  the  Heat  Required. 


COLD  STORAGE  ON  BOARD  SHIP. 


It  is  not  much  over  thirty  years  since  cold  storage  was  first 
introduced,  and  not  so  long  since  the  first  cargo  of  dead  mutton 
was  first  shipped,  yet  an  enormous  industry  has  since  been  built 
up  in  the  transport  of  dead  meat  of  all  kinds,  from  countries 
such  as  the  United  States,  Australia,  New  Zealand,  and  the 
Argentine,  where  it  can  be  grown  cheaply,  to  countries  such  as 
the  British  Islands  and  South  Africa,  where  the  conditions  are 
not  so  favorable,  and  where  consumption  is  large  and  increasing. 
The  early  cargoes  of  frozen  meat  were  looked  upon  with  great 
uneasiness  in  some  quarters,  and  it  is  on  record  that  the  Duke 
of  Beaufort  once  wrote  to  The  Times,  stating  that  it  was  flying 
in  the  face  of  Providence  to  use  "such  means  to  preserve  pro- 
duce which  was  never  intended  to  be  preserved  in  that  way." 
In  addition  to  this,  a  large  fruit-carrying  trade  has  grown  up, 
increasing  in  dimensions  every  year,  which  enables  those  who 
reside  in  the  northern  hemisphere  to  enjoy  the  fruits  that  are 
being  grown  in  the  southern,  at  the  time  when  their  own  fruits 
are  not  obtainable;  the  fruits  that  are  transported  being  almost 
as  luscious  to  the  taste,  after  a  journey  of  several  thousand  miles, 
as  when  picked  on  the  spot.  In  fact,  some  of  the  fruits  sold 
in  London,  that  have  been  brought  from  Australia  and  Cape 
Colony,  taste  better  than  those  grown  in  England  itself. 

There  is  another  very  useful  office  that  cold  storage  has  per- 
formed for  those  who  go  down  to  the  sea  in  ships — it  has  ena- 
bled fresh  meat  to  be  carried  for  the  whole  of  the  voyage,  quite 


2  COLD  STORAGE  ON  BOARD  SHIP. 

apart  from  the  live  animals  that  can  be  stored;  while  the  dead 
meat,  properly  preserved,  is  often  better  than  that  of  the  live 
animals  carried,  because  it  is  not  subject  to  sea-sickness  and 
other  ailments.  Refrigeration  also  offers  a  means  of  dealing 
with  the  many  problems  in  connection  with  the  service  of  men- 
of-war,  such  as  cooling  the  magazines,  the  men's  quarters,  etc. 

Apart  from  the  actual  ability  to  freeze  meat,  and  other  produce 
that  will  stand  freezing,  and  is  preserved  in  that  condition,  mod- 
ern cold  storage  apparatus  enables  the  engineer  to  maintain  any 
temperature  that  may  be  advantageous  to  the  produce,  and  any 
degree  of  dryness,  which  is  itself  a  most  important  point.  Cold 
storage  preserves  by  arresting  the  decay  that  would  otherwise 
commence  soon  after  the  animal  is  killed,  or  the  fruit  is  removed 
from  the  tree  on  which  it  grows.  What  we  know  as  decay  is 
really  an  organic  chemical  and  bacterial  action,  and,  as  in  all 
actions  of  the  kind,  heat  plays  a  very  important  part  in  this. 
The  presence  of  heat,  up  to  a  certain  temperature,  assists  both 
the  chemical  and  bacterial  actions,  while  its  absence  retards 
them,  hence  the  ability  to  preserve  produce.  But  this  it  not  the 
whole  story. 

Different  substances  demand  different  treatment  in  the  matter 
of  temperature  for  preservation.  Mutton,  lamb,  rabbits,  and 
some  other  meats  or  animals  may  be  frozen  as  hard  as  you  please, 
and  if  carefully  thawed  out  when  required  for  use  are  appar- 
ently little  the  worse;  but  beef,  though  it  can  be  frozen,  and  if 
carefully  thawed  is  quite  eatable,  does  not  command  so  high  a 
price  as  if  merely  "chilled,"  that  is,  reduced  to  a  temperature  a 
little  above  the  freezing  point  of  the  meat,  ijuicy  fruits  also 
must  not  be  frozen,  or  they  are  naturally  spoiled,  from  the  fact 
that,  the  juices  expanding  in  freezing,  the  other  parts  are  injured. 
The  fruit  loses  its  vitality,  its  flavor}  Eggs,  vegetables  and  other 
substances  also  must  not  be  frozen,  for  similar  reasons. 

Again,  there  is  a  great  deal  in  the  matter  of  the  hygroscopic 
State  of  the  atmosphere  in  which  the  produce  is  stored.    If  the 


THE  COLD   STORAGE   PROBLEM.  3 

air  in  the  cold  chambers  carries  moisture,  it  is  likely  to  condense 
upon  the  produce,  and  that  is  bad  from  the  viewpoint  of  pres- 
ervation, as  it  assists  any  chemical  actions  that  have  commenced. 
There  is  also  the  question  of  the  carriage  of  produce,  such  as 
apples  and  onions,  with  distinct  odors  of  their  own,  which  will 
be  communicated  to  other  produce  if  the  air  of  the  chambers 
in  which  the  odorous  produce  is  stored  is  allowed  to  penetrate 
to  the  chambers  containing  other  produce.  But  all  of  this  can 
be  arranged,  and  quite  simply,  by  modern  refrigerating  apparatus. 

r 

THE  COLD  STORAGE  PROBLEM. 

Stated  briefly,  the  cold  storage  problem  on  board  ship  consists 
in  the  transportation  of  the  heat  present  in  the  produce,  and  the 
heat  which  passes  into  the  chamber  in  which  the  produce  is 
stored,  to  the  water  of  the  sea,  or  to  the  atmosphere.  Every 
substance,  whatever  its  temperature  and  whatever  its  composi- 
tion, carries  a  certain  number  of  heat  units,  depending  upon  its 
temperature  and  its  specific  heat. 

A  heat  unit,  or  as  it  is  usually  written,  a  British  Thermal  Unit, 
which  is  one  of  the  standards  of  heat  employed  in  calculations,  is 
the  quantity  of  heat  that  will  raise  the  temperature  of  one  pound 
of  pure  water  through  one  degree  Fahrenheit,  when  at  a  tem- 
perature of  32  degrees  F.  The  specific  heat  of  any  other  sub- 
stance is  the  ratio  which  the  heat  required  to  raise  the  tempera- 
ture of  one  pound  of  the  substance  one  degree  F.  bears  to  that 
required  for  one  pound  of  water.  The  specific  heat  of  water  is 
taken  as  the  unit,  and,  as  that  of  the  great  majority  of  sub- 
stances is  less  than  that  of  water,  their  specific  heats  are  usually 
expressed  as  fractions.  The  specific  heat  of  every  substance 
varies  with  the  condition  it  is  in.  Ice,  for  instance,  has  a  specific 
heat  of  only  0.4,  as  against  1.0  for  water. 

To  reduce  the  temperature  of  any  substance  to  freezing  point, 
therefore,  the  number  of  heat  units  that  have  to  be  removed  is 
found  by  multiplying  the  weight  of  the  substance  in  pounds  by 


4  COLD  STORAGE  ON  BOARD  SHIP. 

the  difference  between  the  temperature  at  which  the  produce  is 
received  and  that  at  which  it  freezes,  and  then  by  the  specific 
heat  of  the  substance.     In  addition  to  this,  nearly  all  produce 
that  is  to  be  stored  in  cold  chambers  consists  partly  of  liquids, 
and  when  these  are  reduced  to  the  solid  form,  the  latent  heat 
of  the   liquid  has   to  be   removed  before   it   will   freeze.     With 
ice,  for  instance,  the  latent  heat  of  water  as  a  liquid  has  to  be 
removed;  this  amounts  to  142  units  per  pound.    There  is  usually 
a  still  further  quantity  of  heat  to  be  removed,  for  it  may  be 
necessary  to  hold  the  frozen  masses  a  few  degrees  below  freezing 
point,  so  that  in  case  the  refrigerating  apparatus  does  not  work 
well,  or  if  from  other  causes  the  temperature  to  which  the  sub- 
stance is  exposed  is  raised,  it  will  not  immediately  thaw.     Ice 
that  is  required  for  domestic  or  industrial  purposes  is  reduced 
to  a  certain  number  of  degrees  below  freezing  point,  in  the  pro- 
cess.   Nature  does  exactly  the  same  in  the  production  of  natural 
ice. 

There  is  one  other  point.  The  freezing  point  of  a  liquid  con- 
taining other  substances  in  solution  is  lower  than  that  of  the 
liquid  itself.  Thus  while  the  freezing  point  of  water  is  32 
degrees  F.,  that  of  milk,  and  of  the  blood  and  other  liquids  con- 
tained in  the  carcasses  of  animals,  and  that  of  the  juices  of 
fruits,  is  lower  than  that  of  pure  water.  Hence  with  such  a 
substance  as  mutton,  whose  specific  heat  is  0.69  when  unfrozen, 
and  0.38  when  frozen,  and  the  latent  heat  of  whose  liquids  is  88 
units,  and  which  is  held  at  from  16  to  25  degrees  F.,  the  number 
of  heat  units  to  be  extracted  will  be  found  by  first  multiplying 
the  weight  of  the  liquids  in  the  sheep  in  pounds  (about  62  per- 
cent of  the  total  weight)  by  88,  adding  to  this  the  product  of 
the  total  weight  multiplied  by  0.69  and  by  the  difference  between 
the  temperature  at  which  the  meat  will  be  received  and  its  freez- 
ing point,  and  adding  to  this  again  the  product  of  the  weight 
multiplied  by  0.38,  and  by  the  difference  between  the  temperature 
at  which  the  meat  is  to  be  held  and  its  freezing  point. 


THE  COLD   STORAGE   TROBLEM.  5 

Meat  is  always  allowed  to  cool  to  a  certain  extent  before  taking 
into  store.  As  cold  store  men  and  butchers  express  it,  the  animal 
heat  is  allowed  to  go  off,  this  giving  the  refrigerating  machinery 
so  much  less  to  do.  Where  the  meat  is  beef,  and  is  only  to  be 
chilled,  the  number  of  heat  units  to  be  taken  out  is  much  less 
than  where  it  is  actually  frozen,  as  there  is  no  latent  heat  to  be 
taken  account  of,  and  the  temperature  has  to  be  lowered  only 


CURVE    SHOWING    CAPACITY    OF    AIR    PER    CUBIC    FOOT    FOR    HOLDING 
WATERY    VAPOR. 

to  about  33  or  35  degrees.  In  this  case  the  quantity  of  heat 
units  would  be  found  by  multiplying  the  weight  of  the  meat  by 
0.69,  and  by  the  difference  in  temperature  between  33  or  35  and 
that  at  which  it  was  received. 

This  is  the  first  part  of  the  problem.    The  second  part  of  the 
problem  is  that  of  the  cold  store  itself. 


0  COLD  STORAGE  ON  BOARD  SHIP. 

A  cold  store  is  a  chamber  that  is  built  expressly  to  prevent 
heat  from  passing  from  outside  to  the  produce  inside.  It  is  not 
possible  to  construct  a  chamber  that  will  not  allow  some  heat 
to  pass  through  the  walls,  floor  and  ceiling,  and  this  heat  which 
is  constantly  leaking  through  into  the  chamber  has  to  be  removed, 
just  as  that  of  the  produce  itself  is,  and  transported  to  the  sea 
or  the  atmosphere.  The  quantity  of  heat  that  leaks  through 
depends  upon  the  difference  of  temperature  between  the  inside 
and  outside  of  the  cold  chamber,  upon  the  construction  of  the 
walls,  floor  and  roof,  and  upon  the  extent  of  the  surfaces  exposed 
to  the  action  of  the  heat.  Certain  substances  are  good  thermal 
insulators,  just  as  certain  substances  are  good  electrical  insulators, 
and  the  thermal  insulators  are  used  to  prevent  the  ingress  of 
heat  into  the  cold  chambers,  in  the  same  way  that  electrical  insu- 
lators are  used  to  prevent  the  egress  of  electricity  from  the 
I  conductors.  This  fact  is  very  often  not  understood,  and  is  some- 
times challenged,  because  the  sizes  are  so  different;  but  if  it  be 
borne  in  mind  that  the  thickness  of  the  walls  of  the  chamber 
correspond  with  the  thickness  of  the  insulating  envelope  of  a 
cable,  or  even  of  the  insulation  of  the  iron  core  of  the  armature 
of  a  dynamo  machine,  though  they  are  much  greater,  while  the 
air  inside  the  chamber  corresponds  with  the  copper  or  the  iron, 
it  will  probably  be  appreciated  that  heat  leaks  in  through  the 
thermal  insulator  just  as  electricity  leaks  out  through  the  elec- 
trical insulator. 

Dry,  still  air  is  the  best  insulator  known,  and  the  other  sub- 
stances that  are  good  insulators  owe  their  property  very  largely 
to  the  fact  that  they  contain  a  large  number  of  very  small  air 
cells,  across  which  the  heat  current  has  to  pass.  Air  in  motion 
is  a  bad  insulator.  If  the  air  which  is  confined  in  the  walls  of 
the  cold  chamber  is  able  to  move,  and  to  set  up  convection  cur- 
rents, it  will  by  their  aid  transfer  heat  from  outside  to  inside. 
Moisture  also  is  a  bad  insulator,  and  if  present  will  very  consid- 
erably lower  the  degree  of  insulation, 


THE  COLD  STORAGE  PROBLEM. 


The  importance  of  good  insulation  can  hardly  be  exaggerated. 
It  is  quite  possible,  if  the  insulation  is  sufficiently  bad,  that  the 


SAMPLES    OF    VERTICAL     AND     HORIZONTAL    INSULATION. 

(Black  lines   show   waterproof   insulating  paper.) 

refrigerating  machinery  may  be  grinding  away  uselessly  the  whole 


8  COLD  STORAGE  ON  BOARD  SHIP. 

time,  because  the  heat  will  be  passing  into  the  chamber  as  fast 
as  it  is  being  taken  out.  This  may  be  seen  from  the  following 
example :  Peclet,  an  able  French  savant,  gives  the  rate  of  trans- 
mission of  heat  through  one  inch  of  powdered  wood  charcoal,  one 
of  the  substances  used  in  cold  storage  work,  as  0.63  units  per 
square  foot  per  degree  F.  per  hour.  Take  a  chamber  cubical  in 
form,  12  feet  long  on  the  side,  giving  a  surface  exposed  to  the 
heat  of  864  square  feet,  and  assume  a  difference  of  temperature 
of  50  degrees  F.  This  would  give  a  passage  of  27,216  heat  units 
through  the  walls,  roof  and  floor  on  Peclet's  figures,  per  hour, 
and  would  require  approximately  a  2-ton  machine  to  handle  com- 
fortably. (The  measurement  of  refrigerating  machines,  i-ton, 
2-tons,  etc.,  will  be  explained  later.)  If  we  have,  instead  of  one 
inch  of  the  substance,  six  inches,  as  is  far  more  common,  the 
rate  of  transfer  of  heat  through  the  walls  will  be  approximately 
one-sixth  that  with  the  one-inch,  and  a  machine  designed  for 
a  half  ton  should  easily  deal  with  it.  On  the  other  hand,  if 
the  insulation  is  so  reduced  that  the  rate  of  transmission  through 
it  is  (say)  100,000  units  per  hour,  in  a  room  of  that  size,  the 
whole  power  of  a  machine  designed  for  six  tons  would  be 
required. 

Cold  stores  for  ship  work,  and  for  a  good  many  other  places, 
are  built  up  as  follows :  The  space  to  be  occupied  by  the  cold 
chamber  is  surrounded  by  a  double  wall,  which  should  extend  to 
the  decks,  both  above  and  below,  both  walls  being  formed  of 
wood.  Where  it  can  be  arranged;  and  where  it  is  strong  enough 
to  stand  the  strains  that  are  brought  against  the  walls,  they  are 
built  of  matched  boarding,  securely  nailed  to  uprights,  the  two 
sets  of  uprights  being  braced  together  and  lined  on  the  insides 
(the  sides  facing  each  other),  and  covered  with  waterproof  paper. 
There  are  several  papers  made,  consisting  of  tough  manilla  or 
other  substances,  saturated  with  substances  impervious  to  water 
and  to  the  rays  of  the  sun,  and  these  are  used  to  line  the  space 
in  which  the  insulating  material  is  to  be  placed.     Between  the 


THE  COLD  STORAGE  PROBLEM.  9 

two  walls,  it  will  be  understood,  there  is  a  space,  broken  up  to 
a  certain  extent  by  the  supports  of  the  walls  themselves,  and 
into  this  space  the  insulating  substance  is  poured  and  tightly 
packed.  It  is  of  great  importance  that  the  substance  shall  be 
so  stowed  that  it  cannot  settle,  or  move  in  any  way.  The  division 
of  the  space  by  the  supporting  timbers  assists  in  this.  If  the 
insulation  settles,  leaving  a  space  at  the  top,  convection  air  cur- 


Condenser  Evaporator 

DIAGRAM    OF    COMPRESSOR    CIRCUIT,    WITH    CONDENSER    AND   EVAPORATOR. 

rents  are  set  up,  which  lower  the  insulation,  and  moisture  may 
also  get  in. 

The  best  insulating  materials  are  silicate  cotton,  cork  and 
finely  divided  charcoal.  Silicate  cotton,  or  slag  wool,  as  it  is 
often  called,  is  a  substance  made  from  the  slag  of  iron  smelting 
furnaces.  It  is  very  largely  composed  of  silicon,  and  in  its 
preparation  the  slag  is  remelted  in  a  small  furnace,  to  which 
an  air  blast  is  attached  which  blows  the  molten  slag  into  fine 
hair-like  threads,  or  wool,  something  similar  to  spun  glass.     In 


10  COLD  STORAGE  ON  BOARD  SHIP.  , 

this  condition  it  is  full  of  small  air  cells,  and  when  packed  tight, 
and  moisture  excluded,  it  makes  the  best  insulator  known. 
Finely  divided  wood  charcoal  is  prepared  in  the  process  of  wood 
distillation.  The  wood  that  is  employed  very  largely,  in  the 
United  Kingdom,  is  the  waste  cuttings  from  the  willow  used  in 
the  manufacture  of  cotton  reels.  It  owes  its  property  of  insu- 
lation very  largely  to  the  air  cells  before  mentioned.  It  should 
be  packed  tight,  and  dry.  Cork  in  a  finely  divided  state  is  an- 
other good  insulating  substance.  Cork  is  an  external  growth 
on  particular  kinds  of  oak,  which  grow  in  certain  parts  of  Spain, 
America,  and  a  few  other  countries.  It  contains  a  number  of 
very  fine  cells  with  thin  walls,  all  built  up  together,  very  much 
as  a  honey  comb  is  built  up,  but  with  the  walls  very  much 
thinner  and  the  spaces  much  smaller.  It  is  used  in  a  finely 
divided  or  broken  up  state,  as  the  other  materials  are,  and  also 
in  the  form  of  cork  bricks,  which  can  be  worked  into  any  posi- 
tion required.  The  bricks  have  the  air  cells,  just  as  the  small 
pieces  of  cork  have,  the  latter  having  in  addition  the  air  spaces 
between  the  pieces.  Cork  bricks  have  the  advantage  that  they 
enable  a  much  better  mechanical  job  to  be  made.  With  a  ship 
knocking  about  in  a  sea  way,  this  is  a  matter  of  considerable 
importance,  as,  if  the  walls  are  sprung  and  air  admitted,  the 
insulation  may  be  practically  destroyed. 

There  are  a  number  of  other  substances  that  are  available  as 
insulators.  The  problem,  it  will  be  understood,  is  very  similar 
to  that  of  insulating  steam  pipes,  the  same  materials  being  used 
for  the  two  purposes,  where  they  can  be.  In  the  one  case  the 
object  is  to  prevent  heat  of  the  steam  inside  the  pipes  from 
leaking  out,  while  in  the  other  the  object  is  to  prevent  heat  from 
outside  from  passing  inwards.  There  is  one  important  differ- 
ence that  should  be  noted,  however.  With  high  temperatures, 
still  dry  air  is  the  insulator  par  excellence,  especially  where  it  can 
be  applied  in  small  quantities,  as  in  the  jackets  of  heating  appa- 
ratus; but  with  cold  storage  apparatus  air  has  not  always  such 


THE  COI.D   STORAGE   PROBLEM. 


II 


a  good  name,  though  it  is  acknowledged  to  be  the  best  insulator ; 
the  reason  being,  the  writer  believes,  that  it  is  sometimes  difficult 
to  avoid  convection  currents.  Another  insulator  is  sawdust, 
which  has  been  used  a  great  deal  on  shore.  It  is  a  good  and 
cheap  insulator  if  applied  quite  dry  and  well  shaken  down. 
These  two  points  are  essential,  and  they  are  sometimes  difficult 
to  insure  in  sawdust.     Other  substances  are  asbestos  and  mag- 


DIACRAM     SHOWING     COOI.TNC     WATER     CIRCUIT. 

D.    E. — Condenser    and    Coils.      L. — Refrigerant    Inlet.      N. — Refriger- 
ant   Outlet.       Y. — Water    Circulating    Pump. 


nesia  fiber,  peat,  ashes,  fossil  meal  and  finely  divided  mica.  Felt, 
cow  hair,  infusorial  earth,  cotton  wool,  sheep's  wool — all  are 
used,  to  a  certain  extent,  but  silicate  cotton,  charcoal  and  cork 
are  the  principal  ones. 

In  constructing  the  cold  chambers  on  board  ship,  the  outside 
skin  of  the  insulating  wall  should  be  kept  away  from  the  ship's 
side,  and  from  any  bulkhead  that  is  in  metallic  connection  with 
the  ship,  the  engine  room,  or  stoke  hold.    As  far  as  it  is  possible, 


12  COLD  STORAGE  ON  BOARD  SHIP. 

keep  the  cold  chamber  with  a  layer  of  air  around  it,  but 
arrange  if  possible  that  this  air  be  perfectly  still  and  perfectly 
dry.  The  more  nearly  this  can  be  attained,  the  lower  will  be  the 
cost  of  running  the  apparatus.  The  case  is  exactly  similar  to 
that  of  electricity  and  to  that  of  steam,  though  the  direction  of 
motion  of  energy  has  to  be  reversed.  If  steam  or  electricity  are 
allowed  to  leak  out,  more  coal  has  to  be  consumed  to  make  up 
the  loss,  and  the  accessories  are  more  heavily  worked.  If  heat 
is  allowed  to  leak  into  the  cold  chambers,  more  coal  has  to  be 
consumed  in  carrying  it  away,  and  there  is  also  more  work  on 
the  accessories.  It  is  a  good  plan,  when  the  mechanical  condi- 
tions will  allow  it,  to  divide  the  insulating  wall  into  two  por- 
tions; the  outer  portion  being  simply  an  air  jacket,  and  the  inner 
portion  carrying  the  insulating  substance.  Both  should  be  lined 
with  waterproof  paper.  In  small  cold  stores,  air  jackets  are 
often  used  alone  with  a  waterproof  paper. 

It  was  stated  above  that  the  requirements  as  to  temperature 
varied  very  considerably  with  the  kind  of  produce  carried,  and 
it  follows,  therefore,  that  the  construction  of  the  cold  chambers 
will  vary  though  the  main  lines  will  be  the  same.  For  the  large 
quantities  of  frozen  sheep  for  instance,  that  are  carried  from 
New  Zealand  to  the  London  docks — cargoes  of  100,000  to  120,000 
carcasses  being  carried — the  bulk  of  the  fore  and  after  holds  are 
converted  into  huge  cold  chambers,  much  as  the  holds  are  in 
petroleum  tank  steamers,  except  that  there  is  no  attempt  at 
division  of  the  holds  for  meat  carriage.  Probably  the  carriage 
of  frozen  mutton,  with  the  few  crates  of  frozen  rabbits  which  are 
taken  to  fill  up,  represent  the  simplest  case  of  cold  storage  trans- 
port. Freezing  hard  is  the  order,  and  as  long  as  this  is  carried 
out  there  is  no  trouble,  and  freezing  hard  is  comparatively  easy. 
It  is  only  a  question  of  driving.  The  sheep  are  frozen  near 
where  they  are  killed;  each  is  enveloped  in  a  loose  linen  bag, 
with  the  owner's  mark  on  it,  and  they  are  stowed  in  rows  and 
tiers  in  the  holds.     No  harm  can  come  to  them,  so  long  as  the 


THE  COLD  STORAGE  PROBLEM. 


13 


temperature  is  maintained  at  a  certain  low  figure,  and  this  is 
easy  to  accomplish,  provided  that  everything  has  been  properly 
carried  out  in  the  matter  of  insulation.  It  is  like  the  case  of 
the  ship  which  has  only  to  drive  as  hard  as  its  engines  and  boilers 
will  allow  it,  without  thinking  of  the  cost.  If  the  insulation  is 
good,  and  even  if  it  is  only  moderate,  low  temperatures  mean 
simply  more  coal  and  accessories  than  higher  temperatures. 


DIAGRAM     SHOWING    CIRCUIT     OF    REFRIGERANT. 

A. — Compressor.  B.  C. — Piston  and  Rod.  D.  B. — Condenser  and 
Coils.  F.  G. — Evaporator  and  Coils.  H. — Expansion  Valve.  K.  L,  M, 
N. — Delivery   Pipes. 


It  is  when  we  come  to  the  cases  where  certain  definite  tempera- 
tures have  to  be  maintained  that  the  difficulties  of  the  problem 
begin  to  appear.  With  "chilled"  beef,  for  instance,  which  must 
not  be  frozen,  but  is  held  at  about  33  to  35  degrees  R,  the  outer 
layers  will  freeze  if  a  much  lower  temperature  is  reached,  and  the 
condition  of  the  meat  on  arrival  may  be  seriously  deteriorated. 
On  the  other  hand,  if  the  temperature  is  allowed  to  rise  to  an 


14  COLD  STORAGE  ON  BOARD  SHIP. 

appreciable  extent,  the  processes  of  decay,  which  the  low  tem- 
perature holds  in  check,  may  commence,  and  it  is  then  very 
difficult  to  arrest  them,  particularly  as  in  some  cases  the  pro- 
cesses themselves  generate  heat.  Further,  if  one  quarter  of  beef 
commences  to  decay,  the  others  may  take  it  up.  When  first 
received,  the  meat  has  to  be  very  gradually  and  carefully  "chilled," 
or  the  outer  layers  may  be  chilled  while  the  inside  is  still  warm ; 
and  the  inside  meat  being  protected  by  the  outer  layers,  the 
processes  of  decay  may  be  continued  somewhat  vigorously.  The 
meat  is,  therefore,  allowed  to  lose  its  animal  heat,  is  then  very 
carefully  chilled,  so  that  the  process  goes  right  in  to  the  bone, 
and  is  then  maintained  at  the  desired  temperature. 

For  this  purpose,  in  one  arrangement  the  cold  chamber  is 
divided  into  bays,  or  longitudinal  divisions,  to  each  of  which  is 
assigned  its  own  brine  cooling  pipe,  or  two  bays  may  have  a 
stack  of  pipes  fixed  vertically  between  them,  the  flow  in  all  the 
pipes  being  controlled  by  valves  on  the  outside  of  the  chamber. 
Thermometers  are  fixed  in  the  flow  and  in  the  return  pipes,  so 
that  the  attendant  can  learn  what  is  going  on  in  each  bay,  and 
can  allow  the  brine  to  flow  in  that  set  of  pipes  accordingly.  In 
the  case  of  fruit,  it  is  necessary  that  there  shall  be  a  gentle  cur- 
rent of  dry  air  all  around  each  fruit  throughout  the  voyage. 
Fruit  ships  are,  therefore,  fitted  something  on  the  lines  of  frozen 
mutton  carriers,  but  usually  with  air  cooling  only. 

METHODS   OF  COOLING  THE  COLD  CHAMBERS. 

We  will  now  examine  the  method  by  which  the  cold  is  con- 
veyed to  the  chambers.  Having  made  a  box,  so  to  speak,  into 
which  heat  is  to  a  certain  extent  prevented  from  entering,  how 
is  the  low  temperature  to  be  produced  in  the  box,  and  how  is  the 
heat  that  does  pass  through  the  walls  of  the  box  to  be  carried 
away?  For  shipboard  work  the  following  methods  are  permissi- 
ble :  the  use  of  brine,  the  direct  use  of  carbonfc  acid  where  it  is 
v  V 


METHODS  OF  COOLING  THE  COLD  CHAMBERS. 


15 


the  refrigerating  agent,  and  the  use  of  cooled  air.  With  brine 
and  with  carbonic  acid  directly  employed,  pipes  are  laid  in  the 
chamber  to  be  cooled,  usually  in  the  form  of  a  grid,  sometimes 
on  the  side,  sometimes  overhead,  sometimes,  as  mentioned  above, 
a  grid  of  pipes  separates  two  bays,  and  sometimes  the  pipes  are 
formed  into  a  wall.  The  length  and  size  of  the  pipes  are  calcu- 
lated from  the  quantity  of  produce  that  is  to  be  stored,  and  the 
leakage  into  the  chamber  that  may  be  expected.     With  brine 


/ 


DIAGRAM     SHOWING    BRINE    CIRCUIT. 

F.  G. — Evaporator  and  Coils.  K. — Refrigerant  Outlet.  M. — Refrig- 
erant Inlet.  O.- — Brine  Grid  in  Cold  Chamber.  P. — Brine  Discharge 
Pipe.     Q. — Brine   Pump.     R. — Brine   Pipe  Leading  to  Grid, 


cooling,  brine  is  kept  in  circulation  in  the  pipes.  The  brine  may 
consist  of  salt  water — not  sea  water,  but  water  in  which  common 
salt  has  been  dissolved — but  it  more  often  consists  of  a  solution 
of  chloride  of  calcium. 

It  was  mentioned  above  that  dissolving  a  substance  in  water 
lowers  the  freezing  point  of  the  solution,  and  that  is  the  reason 
why  brine  is  used.  One  percent  of  common  salt  in  water  reduces 
the  freezing  point  to  30.5  degrees  F.,  3  percent  brings  it  to  27.8 


1 6  COLD  STORAGE  ON   BOARD  SHIP. 

degrees,  5  percent  to  25.2  degrees,  and  so  on.  One  percent  of 
chloride  of  calcium  lowers  the  freezing  point  to  31  degrees  F., 
5  percent  to  27.5  degrees,  10  percent  to  22  degrees,  15  per- 
cent to  15  degrees,  20  percent  to  5  degrees,  and  25  percent  to 
— 8  degrees.  Common  salt  is  not  used  now,  except  in  special 
cases,  for  reasons  that  need  not  be  mentioned  to  marine  engineers. 
A  20-percent  solution  of  calcium  chloride  is  usually  employed, 
or,  if  especially  low  temperatures  are  required,  a  25-percent 
solution. 

The  use  of  a  liquid  that  freezes  at  temperatures  below  that  at 
which  the  produce  is  to  be  held  is  necessary.  The  brine  itself 
is  cooled  by  one  of  the  processes  that  will  be  described,  and  it 
is  caused  to  circulate  continually  from  the  tank  in  which  it  is 
cooled,  through  the  pipes  connecting  it  with  (and  forming)  the 
grid  in  the  cold  chamber,  and  back  to  the  tank  again.  In  passing 
through  the  grid  in  the  cold  chamber  it  absorbs  heat  from  the  air 
in  the  chamber,  which  in  its  turn  takes  heat  from  the  produce, 
and  so  on.  Heat  flows  from  bodies  at  higher  temperatures  to 
those  at  lower  temperatures,  and  as  the  entering  brine  is  at  a 
lower  temperature  than  the  air  in  the  room  it  is  to  cool,  heat 
flows  to  it.  The  brine  in  the  return  pipe  is,  therefore,  at  a  higher 
temperature  than  that  in  the  supply  pipe,  and  as  the  brine  which 
passes  through  it,  back  to  the  evaporating  tank  where  it  is 
cooled,  is  at  a  higher  temperature  than  its  surroundings  in  the 
evaporating  tank,  heat  again  flows  from  it  to  the  refrigerating 
agent.  As  explained  in  connection  with  the  apparatus  for 
"chilled"  beef,  the  attendant  knows  by  the  difference  between  the 
temperature  of  the  flow  and  that  of  the  return  brine  pipes  of 
each  particular  section  of  the  chamber  what  work  in  the  matter 
of  cooling  is  going  on,  and  this  applies  also  to  each  chamber. 
It  is  not  a  difficult  calculation  to  determine  the  quantity  of  brine 
that  must  pass  through  a  particular  cold  chamber  in  a  certain, 
time,  to  keep  the  chamber  at  the  required  temperature  or  to 
reduce  the  produce  to  its  keeping  temperature — having  given  the 


METHODS  OF  COOLING   THE  COLD  CHAMBERS.  VJ 

number  of  heat  units  to  be  carried  away  in  the  same  time,  ascer- 
tained in  the  manner  explained  above. 

A  20-percent  solution  of  calcium  chloride  has  a  specific  gravity 
of  1.18,  so  that  a  gallon  (Imperial)  of  the  solution  weighs  n.8 
pounds.  The  specific  heat  of  the  solution  is  0.834,  therefore  each 
gallon  that  passes  through  the  pipes  carries  off  9.84  heat  units 
for  each  degree  F.  that  its  temperature  is  raised.  Brine  is  usually 
worked  with  an  increase  of  temperature  of  from  6  to  8  degrees 


FT~ 

<— 

z 

" — 

X 

^5^»° 

X 

X 

v     ; 

Bl 

s-C 

a 

X 

X 

\ 

L_ 

DIAGRAM     SHOWING     AIR     CIRCUIT. 

O. — Brine  Grid  in  Cold  Chamber.  P. — Pipe  from  Evaporator  Tank. 
R. — Pipe  to  Expansion  Tank.  5.— Fan.  U. — Cold  Air  Duct.  V .— Cham- 
ber  to    be    Cooled.      X.X.— Air   Ports.      Z.— Exhaust   Air   Duct. 


F.  between  the  entrance  and  outgoing  ends  of  the  grids,  hence  if 
we  take  an  average  rise  of  4  degrees,  since  the  temperature  of 
the  brine  will  be  continually  rising  as  it  passes  through  the  pipes, 
each  gallon  will  carry  off  39.36  heat  units.  The  pipe  used  for 
brine  cooling  ranges  from  i-inch  bore  to  2  inches.  The  external 
diameter  of  a  i-inch  pipe  is  1.3  inches,  while  that  of  a  2-inch  pipe 
is  2.4  inches  (about).  The  mean  surface  of  pipe  exposed  to  the 
heat  will  be,  in  the  case  of  the  i-inch,  43.3  square  inches  per 
running  foot  of  pipe,  and  that  of  the  2-inch  pipe  83  square 
inches  per  running  foot. 


i8 


COLD  STORAGE  ON  BOARD  SHIP. 


If  we  take  Peclet  again  as  a  guide,  we  can  calculate  approxi- 
mately the  number  of  heat  units  that  will  pass  through  from  the 
air  into  the  brine  in  any  given  time.  He  gives  230  as  the  number 
of  heat  units  per  square  foot  of  surface  that  will  pass  through 
one  inch  thickness  of  iron,  in  one  hour,  with  a  difference  of 
temperature  of  one  degree  F.  The  thickness  of  i-inch  bore  iron 
pipe  is  approximately  1/8  inch,  and  of  2-inch  pipe  1/7  inch, 
hence  the  rate  of  passage  of  heat  through  the  walls  of  the  pipe 
should  be  respectively  1,840  and  1,610  units  per  hour  per  square 
foot  for  every  degree  of  rise  in  temperature  of  the  brine,  or 
again  928  units  per  running  foot  with  2-inch  pipe,  and  550  with 
I-inch  pipe.  In  practice  the  grid  is  made  longer  than  would  be 
apparently  necessary,  and  more  surface  is  exposed  to  the  action 
of  the  heat,  in  order  that  the  brine  may  flow  at  a  lower  veloc- 
ity, and  also  because  the  results  obtained  in  service  do  not 
usually  come  up  to  laboratory  tests. 

There  is  an  important  point  in  connection  with  this.  Power, 
it  will  have  been  observed,  is  required  for  abstracting  the  heat 
and  carrying  it  away.  Where  brine  cooling  is  employed,  power 
is  required  to  keep  the  brine  in  circulation,  and  this  power  is  in 
direct  proportion  to  the  extent  of  the  wetted  surface  of  the  pipe, 
and  to  the  square  of  the  velocity  at  which  the  brine  is  flowing. 
Hence  it  will  be  seen  that  it  would  not  be  difficult  to  add  appre- 
ciably to  the  power  required  by  the  plant  as  a  whole  by  giving  the 
brine  a  high  velocity.  Practice  as  usual  has  solved  the  question 
for  itself,  by  the  usual  methods,  and  the  following  figures  may 
be  taken  as  the  latest :  A  cubical  space  such  as  that  taken,  12 
feet  on  the  side,  if  well  insulated,  requires,  to  be  held  at  32 
degrees  F.,  the  temperature  for  "chilled"  beef  and  some  other 
substances,  a  length  of  about  432  feet  of  i-inch  pipe,  and  about 
half  that  length  of  2-inch  pipe,  with  roughly  proportionate  lengths 
of  intermediate  sizes.  Small  rooms  require  more  pipe  in  propor- 
tion than  large  rooms.  Thus  with  rooms  under  1,000  cubic  feet 
capacity  400  feet  of  i-inch  pipe  and  half  that  length  of  2-inch 


METHODS    OF    COOLING    THE    COLD    CHAMBERS.  19 

pipe  is  given ;  while  for  cold  chambers  of  over  10,000  cubic  feet 


capacity  200  feet  of  i-inch  pipe  and  half  that  length  of  2-fnch 
is  given,  in  each  case  per  1,000  cubic  feet. 


20  COLD   STORAGE   ON    BOARD   SHIP. 

For  lower  temperatures,  again,  longer  lengths  of  oipe  are 
required,  and  approximately  in  the  following  proportions:  tor  a 
temperature  of  10  degrees  F.,  double  the  lengths  of  pipe  are 
required  that  are  given  for  32  degrees  F.,  and  for  zero  F.  tem- 
perature about  three  times  that  given  for  10  degrees.  The  velocity 
of  the  brine  is  usually  kept  at  or  below  3  feet  per  second.  A 
high  velocity  has  another  serious  drawback,  unless  large  pipes 
are  employed — all  fluids  flowing  through  pipes  create  friction, 
which  generates  heat,  and  consequently  by  raising  the  tempera- 
ture of  the  brine  lowers  its  ability  to  carry  off  heat  from  the 
room  it  is  to  cool.  Brine  coils  are  made  in  various  lengths, 
according  to  the  work  they  are  to  perform  and  the  sizes  of  the 
pipes,  from  100  feet  with  small  pipes,  for  low  temperatures,  up 
to  1,000  feet  with  2-inch  pipes,  and  higher  temperatures. 


DIRECT  EXPANSION. 

By  direct  expansion  is  meant  the  direct  action  of  the  refrig- 
erating agent,  usually  carbonic  acid  gas,  on  board  ship,  except 
where  compressed  air  is  employed  in  the  chamber  to  be  cooled. 
As  will  be  explained,  the  refrigerant  is  caused  to  assume  alter- 
nately the  liquid  and  the  gaseous  state.  A  compressor  and  other 
apparatus  are  employed  to  reduce  it  to  the  liquid  state,  in  which 
condition  it  is  conveyed  to  the  expansion  coils,  consisting  of 
pipes  very  similar  to  those  that  have  been  described  for  the 
brine.  The  anhydrous  liquid,  on  passing  into  the  expansion  coils, 
being  suddenly  released  from  the  pressure  under  which  it  is  held, 
is  reformed  into  gas;  but  as  a  liquid  can  become  a  gas  only  by 
the  addition  of  the  latent  heat  of  the  gas,  it  abstracts  this  heat 
from  surrounding  objects,  such  as  the  brine  with  which  the 
expansion  coils  are  in  contact,  in  the  brine  tank,  or  from  the  air 
of  the  chamber  in  which  the  coils  are  placed,  where  direct  expan- 
sion is   employed.     The  action,  so  far  as   the  cooling  of  the 


DIRECT   EXPANSION. 


21 


chamber  and  the  produce  is  concerned,  is  exactly  the  same  as 
with  brine  cooling. 


•japi  auug 


•?9nno  3U?ja 


There  is  a  difference  of  temperature  between  the  pipe  contain- 
ing the  refrigerant  and  the  air  surrounding  the  pipe,  because  the 


22  COLD    STORAGE    ON  "BOARD    SHIP. 

refrigerant  has  been  lowered  in  temperature,  immediately  on  its 
entrance  into  the  expansion  coils, -by  the  evaporation  of  a  small 
portion  of  itself.  Heat  passes  from  the  air  of  the  chamber  to  the 
surface  of  the  pipe,  and  thence  through  the  pipe  to  the  refrig- 
erant, this  heat  enabling  more  of  the  liquid  to  evaporate,  abstract- 
ing more  of  the  heat  from  the  air,  and  so  on.  Heat  passes  from 
the  produce  to  the  air  surrounding  it,  so  long  as  any  difference 
cf  temperature  exists  between  them,  and  hence  the  produce  and 
the  air  of  the  chamber  are  kept  at  the  temperature  required,  by 
the  aid  of  the  direct  evaporation  of  the  refrigerant,  just  as  by 
the  circulation  of  the  brine.  The  refrigerant  is  maintained  in 
continual  circulation,  just  as  the  brine  is;  for  the  compressor, 
which  performs  also  the  duty  of  a  pump,  causes  it  to  be  con- 
tinually passing  from  the  condenser  to  the  evaporator  coils,  thence 
to  the  compressor,  and  to  the  condenser  again,  as  will  be 
described. 

The  passage  of  the  refrigerant  into  the  evaporator  coils  is  con- 
trolled by  an  expansion  valve,  which  is  practically  a  stop  valve  of 
particular  construction.  By  its  aid  more  or  less  of  the  liquid 
refrigerant  is  allowed  to  pass  into  the  expansion  coils.  The 
length  of  the  latter  can  be  found  by  calculation  and  has  also  been 
determined  by  practice,  though  the  calculation  is  somewhat  dif- 
ferent from  that  for  the  length  of  brine  coils.  Each  pound  of 
each  kind  of  refrigerant  absorbs  a  certain  number  of  heat  units, 
in  passing  from  the  liquid  to  the  gaseous  condition,  the  number 
of  units  absorbed  varying  with  the  temperature  and  the  pressure. 
Carbonic  acid  absorbs  about  no  heat  units  per  pound  at  the 
usual  evaporator  pressure,  in  temperate  climates,  while  at  higher 
pressures  a  smaller  quantity  is  absorbed,  86  units  at  650  pounds 
pressure,  and  66  units  at  800  pounds  pressure.  The  temperatures 
corresponding  to  these  pressures  are  32,  50  and  68  degrees  F. 
At  lower  temperatures  the  pressures  are  lower,  380  pounds  at 
14  degrees  F.,  and  288  pounds  at  —4  degrees  F. 

At  32  degrees  F.,  and  the  pressure  given  above,  one  pound  of 


DIRECT   EXPANSION.  23 

carbonic  acid  measures  0.167  cubic  feet,  or  a  cubic  foot  weigns 


approximately  6  pounds.     It  will  be  understood  that  volumes 


<f<|  COLD    STORAGE    ON    BOARD    SHIP. 

of  gaseous  substances  that  are  pumped  to  and  fro  have  to  be 
dealt  with,  rather  than  weights.  One  cubic  foot  of  carbonic  acid 
will,  therefore,  absorb  about  660  heat  units  in  passing  from  the 
liquid  to  the  gaseous  condition  at  32  degrees  F.  The  gaseous 
carbonic  acid  formed  from  the  liquid  also  carries  off  a  certain 
quantity  of  heat,  just  as  the  brine  does,  but  it  is  bad  engineering 
to  allow  much  of  this  to  be  done.  The  specific  heat  of  carbonic 
acid  gas  is  0.2167,  so  that  while  one  cubic  foot  of  the  liquid,  in 
expanding  to  a  gas,  abstracts  660  heat  units,  the  same  quantity 
of  the  gas,  in  passing  through  the  remaining  pipes  of  the  expan- 
sion coils,  will  absorb  only  1.3  units,  for  every  degree  of  difference 
in  temperature  between  it  and  the  atmosphere  of  the  room. 

With  direct  expansion  the  lengths  of  the  pipes  will  be  much  less 
than  with  brine.  Ammonia  and  sulphurous  acid  are  employed 
as  refrigerants,  but  there  is  the  great  objection  to  direct  expan- 
sion with  ammonia,  that  the  escape  of  a  small  quantity  of  the 
gas,  in  the  cold  chamber,  may  seriously  affect  the  produce.  Sul- 
phurous acid  does  not  labor  under  that  objection,  for  the  sub- 
stance itself  is  used  as  a  disinfectant,  but  it  has  not  so  far  been 
much  employed  on  board  ship.  The  calculation  for  the  quantity 
of  the  other  refrigerants,  and  the  size  and  length  of  the  pipes,  is 
practically  the  same,  using  different  constants,  as  with  carbonic 
acid.  Ammonia  absorbs  555.5  units  per  pound  at  o  degrees  F., 
while  sulphurous  acid  absorbs  171.2  per  pound.  It  will  be  under- 
stood that  the  gas  which  is  formed  is  pumped  through  the  grid 
of  pipes,  and  thence  to  the  compressor,  to  be  reconverted  into 
liquid,  so  that  the  friction  of  the  gas  in  the  pipes  has  to  be 
taken  into  account,  in  the  same  way  as  the  friction  of  the  brine, 
and  it  follows  the  same  laws,  depending  upon  the  surface  of  the 
pipe  rubbed  over  by  the  gas,  and  upon  the  velocity  at  which  the 
gas  travels.     A  low  velocity  is  of  some  value  here. 


COOLING    THE   CHAMBER   BY    COOLING.   THE   AIR. 


3f 


BRUNSWICK    ONS-TON    COMPRESSOR. 


COOLING  THE  CHAMBER  BY  COOLING  THE  AIR. 

This  is  the  more  frequent  method  adopted  where  fruit  is  car- 
ried, and  it  is  the  method  that  is  coming  more  and  more  into 
vogue  on  shore,  wherever  it  can  be  arranged.  It  enables  the 
engineer  to  have  a  greater  command  over  his  work.  But  before 
describing  the  arrangements  for  this,  another  important  matter, 
the  ventilation  of  cold  chambers,  a  matter  leading  directly  to  the 


26  COi,D   STORAGE   ON   BOARD   SHIP. 

process  of  cooling  the  air  entering  the  chamber,  should  be  con- 
sidered. The  proper  ventilation  of  cold  chambers  is  a  very 
troublesome  problem,  and  it  is  the  troubles  encountered  in  con- 
nection with  this  which,  the  writer  believes,  have  led  very  largely 
to  development  in  the  direction  of  cooling  the  air  itself. 

In  all  cold  chambers  in  which  produce  is  stored  a  certain  quan- 
tity of  carbonic  acid  gas  is  formed,  and  other  gases  are  also 
given  off,  which  are  more  or  less  deleterious  to  the  produce,  and 
should  therefore  be  kept  at  as  low  a  percentage  as  possible.  But 
the  air  which  is  laden  with  these  gases  can  be  got  rid  of  only 
by  allowing  other  air  to  enter  and  take  its  place,  while  the 
cleansing  action  that  is  advisable — the  action  of  air  in  the  process 
of  ventilation  is  very  similar  to  that  of  water  in  the  ordinary 
processes  of  cleansing — demands  that  the  fresh  air  shall  be  al- 
lowed to  penetrate  to  every  part  of  the  chamber,  and  to  reach 
every  surface  of  the  produce.  But  if  outside  air  is  admitted, 
it  is  usually  at  a  higher  temperature  than  that  inside  the  cham- 
ber— there  are  exceptions  which  will  be  noted — and  the  incoming 
air  brings  heat  with  it.  This  may  not^e  a  serious  matter,  where 
it  is  known  and  provided  for.  Every  time  the  door  of  the  cham- 
ber is  opened,  to  put  in  or  take  out  produce,  or  for  the  entrance 
or  exit  of  the  attendant,  the  same  thing  happens,  to  an  extent 
depending  upon  the  construction  of  the  doors  and  the  care  of 
the  attendant. 

In  many  cases  no  other  provision  is  made  for  ventilation,  but 
the  best  practice  provides  for  its  being  carried  out  in  a  thor- 
oughly scientific  manner,  and  in  such  a  manner  as  to  assist  the 
convection  currents  that  are  of  so  much  use  in  distributing  the 
cooling  influence  of  the  brine  or  expansion  grid.  Wherever  the 
grid  is  placed,  it  will  be  understood,  the  air  in  its  immediate 
neighborhood  will  feel  the  effect  first,  and  this,  becoming  heavier 
as  it  cools,  will  tend  to  fall,  allowing  the  lighter  air  to  take  its 
place.  In  some  cases  the  convection  currents  so  set  up  are  hardly 
sufficient   to   distribute   the   cooling   effect   of   the   pipes   to   the 


COOLING    THE   CHAMBER    BY    COOLING    THE    AIR.  27 

produce  efficiently,  and  this  leads  to  a  larger  expenditure  of  coal 
and  accessories.  Where  the  grid  is  placed  on  the  side  of  the 
chamber,  for  instance,  the  convection  currents  are  sometimes  very 
sluggish.  The  ventilation  and  the  convection  currents  are 
assisted  by  fans,  placed  in  any  convenient  position,  driven 
by  any  convenient  source  of  power,  usually  electric  motors. 
The  fans  are  arranged  either  to  suck  the  air  out  of  the 
chamber,  an  inlet  being  provided  in  another  part,  at  a  distance 
from  the  outlet,  or  to  force  the  air  into  the  chamber,  an  outlet 
being  provided  at  the  other  end.  The  outlet  should  be  a  little 
above  the  floor  line,  in  the  great  majority  of  cases,  as  the  car- 
bonic acid  gas  is  heavier  than  air,  while  the  inlet  should  be  near 
the  ceiling,  at  the  opposite  end.  Fans  should  be  arranged  to 
assist  the  circulation  of  the  air  in  the  chamber,  apart  from  the 
outside  circulation. 

The  actual  arrangement  will  vary  with  each  case,  and  the 
engineer  in  charge  will  have  to  be  guided  by  the  condition  of  the 
cold  rooms.  In  some  cases  the  fan  may  be  kept  running  con- 
tinually to  assist  the  convection  currents  within  the  chamber, 
there  being  no  ingress  of  air  to  the  chamber  except  at  certain 
fixed  times  and  for  certain  limited  periods,  and  the  entrance  of 
the  outside  air  being  controlled  by  valves,  opened  from  the  out- 
side. In  a  few  cases  it  is  possible  to  allow  a  small  current  of  air 
to  pass  through  the  chamber  all  the  time,  remembering  that  it 
brings  heat  with  it,  and  that  the  heat  so  brought  must  be  ab- 
stracted, and  further  that  it  will  be  in  proportion  to  the  differ- 
ence in  temperature  between  the  air  from  which  the  supply  is 
taken  and  that  of  the  chamber.  The  incoming  air  will  bring 
moisture,  which  again  must  be  abstracted,  and  this  means  the 
further  abstraction  of  heat. 

The  quantity  of  heat  brought  in  by  the  incoming  air  is  found 
by  multiplying  the  quantity  of  air  passing  in  by  the  difference 
in  temperature  between  it  and  the  air  of  the  chamber,  and  by 
the  specific  heat  of  air.     We  may  take  the  specific  heat  of  air 


28  COLD    STORAGE    ON    BOARD    SHIP. 

as  0.2,  it  being  neither  at  constant  volume,  nor  at  constant  pres- 
sure. The  weight  of  a  cubic  foot  of  dry  air  at  60  degrees  is 
approximately  0.08  pound,  so  that  there  are  12.5  cubic  feet  of 
air  in  one  pound,  and  one  heat  unit  will,  therefore,  raise  the 
temperature  of  62.5  cubic  feet  of  air  one  degree  F.  Conversely, 
air  which  is  at  a  temperature  of  60  degrees  F.,  entering  a  cold 
chamber  in  which  the  temperature  is  say  10  degrees,  will  bring 
50  heat  units  with  every  62.5  cubic  feet,  or  one  heat  unit  with 
every  1.25  cubic  feet,  and  with  a  chamber  of  10,000  cubic  feet 
capacity  it  would  require  the  services  of  a  machine  capable  of 
producing  a  ton  of  refrigeration  in  twenty-four  hours,  to  deal 
with  this  in  one  hour,  or  a  proportionately  larger  machine  if  it 
had  to  be  dealt  with  in  a  shorter  time ;  and  this  does  not  take 
any  account  of  the  moisture  brought  in.  The  question  whether 
this  extra  work  shall  be  taken  is  one  for  consideration  on  the 
lines  of  the  balance  sheet.  On  one  side  should  be  put  the  dete- 
rioration of  the  produce,  if  any,  that  will  take  place  if  the  store 
is  not  ventilated,  and  on  the  other  the  ^ost  of  the  additional  work 
involved  in  the  removal  of  the  additional  heat. 

Another  important  point  must  not  be  last  sight  of — the  effect 
of  the  increased  temperature  upon  the  produce — but  again  this 
is  a  matter  for  careful  regulation.  The  figures  required  are : 
how  much  air  comes  in,  how  much  heat  it  brings  with  it,  and 
how  quickly  the  heat  must  be  removed.  This  enables  the  work 
required  to  be  calculated. 

COOUNG   THE   AIR  ENTERING   COLD  CHAMBERS. 

There  are  really  two  parts  to  the  problem  involved  in  cooling 
a  chamber  by  cooling  the  air  which  enters  it.  There  is  the 
removal  of  the  heat  of  the  air  itself,  in  order  to  reduce  it  to 
the  temperature  at  which  the  air  in  the  chamber  is  to  be  held; 
and  there  is  the  removal  of  the  moisture  held  in  suspension  in 
the  air.     Both  objects  are  accomplished  at  one  operation,  and 


COOUNO    THE    AIR    ENTERING    COLD    CHAMBERS. 


29 


both  involve  the  abstraction  of  a  certain  number  of  heat  units. 
Atmospheric  air  always  holds  moisture  in  suspension,  the  quan- 


rr 


tity  held  depending  upon  the  temperature,  and  increasing  very 
rapidly  as  the  temperature  increases.  But  the  moisture  in  sus- 
pension is  in  the  condition  of  vapor,  and  it  can  assume  that 


30  COLD    STORAGE    ON    BOARD    SHIP. 

condition  only  by  absorbing  a  certain  quantity  of  heat,  from  900 
to  1,000  units  for  every  pound  of  water  vaporized.  The  method 
of  cooling  wine  by  wrapping  a  wet  towel  around  the  bottle  and 
putting  it  in  the  sun  is  well  known;  while  the  case  of  a  man's 
wet  clothes  drying  on  his  back  and  giving  him  a  cold,  will  per- 
haps be  more  familiar.  In  both  cases  the  heat  necessary  for 
evaporation  is  taken  largely  from  the  object  upon  which  the 
damp  fabrics  are  placed.  In  order,  therefore,  that  the  vapor 
held  by  the  air  shall  be  deposited,  the  latent  heat  of  evaporation 
must  be  abstracted  from  it.  The  mere  fact  of  cooling  a  certain 
quantity  of  air  leads  to  the  air's  seeking  to  get  rid  of  a  portion 
of  its  moisture,  and  its  deposition  will  lead  to  a  rise  of  its 
temperature,  owing  to  the  delivery  of  heat  by  the  vapor. 

There  is  another  factor  in  the  problem  of  the  deposit  of  the 
watery  vapor  from  the  air.  The  question  arises,  when  will  the 
vapor  be  deposited,  and  why?  The  capacity  of  air  for  absorbing 
the  vapor  of  water  varies,  as  shown  in  the  accompanying  curve. 
But  the  air  is  very  rarely  saturated  with  vapor,  that  is,  it  very 
rarely  carries  the  full  quantity  of  which  it  is  capable,  at  any 
given  temperature.  In  damp  climates,  in  the  winter  months,  it 
may  carry  as  much  as  85  or  90  percent  of  the  quantity  it  would 
carry  if  saturated;  while  in  dry  climates,  from  50  to  65  percent 
only  will  be  carried. 

Evaporation  is  constantly  going  on  at  all  temperatures,  from 
the  surface  of  any  liquid  exposed  to  the  air,  and  from  any 
objects,  such  as  dress  fabrics,  wood,  etc.,  in  which  liquids  are 
held.  So  the  air  above  and  resting  upon  the  surface  of  a  liquid 
carries  a  certain  quantity  of  vapor.  This  exerts  a  certain  pres- 
sure upon  the  surface  of  the  liquid,  apart  from  that  due  to  the 
weight  of  the  air  itself,  while  the  vapor  which  is  being  given 
off  from  the  surface  of  the  liquid  also  exerts  a  certain  pressure 
upon  the  vapor  already  in  the  atmosphere  above.  The  pressure 
of  the  vapor  coming  away  from  the  liquid  depends  upon  the  tem- 
perature of  the  liquid,  while  the  pressure  of  the  vapor  in  the  air 


COOUNG    THE    AIR    ENTERING    COLD    CHAMBERS. 


31 


above  depends  upon  the  temperature  of  the  air,  and  the  percent- 
age of  possible  vapor  carried.  If  the  air  and  liquid  are  at  the 
same  temperature,  and  the  air  is  saturated  with  vapor,  no  evap- 
oration can  take  place,  as  the  pressure  of  the  vapor  already  in  the 


«ffi 


BROWN-COCHRAN      CARBONIC      ANHYDRIDE      COMPRESSOR. 


atmosphere,  and  of  that  issuing  from  the  liquid,  are  equal.  But 
where,  as  is  nearly  always  the  case,  the  air  is  not  saturated,  evap- 
oration will  go  on  until  the  pressures  of  the  two  vapors  are 
equal.  The  converse  of  the  above  is  also  true.  Where  there  is 
a  difference  between  the  pressure  of  the  vapor  in  the  atmosphere 
and  that  of  the  vapor  rising  from  some  body  with  which  it  is  in 


32  COLD   STORAGE  ON   BOARD   SHIK 

contact,  in  favor  of  the  atmospheric  vapor,  the  vapor  will  be 
deposited  from  the  atmosphere,  provided  that  it  can  deliver  up 
its  heat  of  vaporization  to  the  surrounding  objects. 

Bearing  in  mind  the  fact  that  the  capacity  of  air  for  carrying 
vapor  rises  rapidly  with  the  temperature,  it  follows  that  any 
lowering  of  the  temperature  of  the  air  immediately  tends  to  in- 
crease the  percentage  of  saturation,  and  to  increase  the  vapor 
pressure,  and  its  tendency  to  deposit.  The  vapor  pressure  is 
obtained  by  first  finding  the  percentage  of  saturation  of  the  air, 
by  the  wet  and  dry  bulb  thermometer;  and  then  consulting  a 
table  that  has  been  compiled  from  observation.  From  another 
table,  also  compiled  from  observation,  the  vapor  pressure  at  sat- 
uration at  different  temperatures  is  obtained,  the  actual  pressure 
of  the  vapor  in  the  air,  at  the  temperature  to  which  it  is  reduced, 
being  determined  from  these  two  tables,  and  the  thermometer 
readings.  The  vapor  pressure  of  the  ice  or  snow  on  the  brine 
or  expansion  grids  used  in  cooling  the  air,  as  explained  below,  is 
also  known,  from  its  temperature — vapor  is  coming  away  from 
even  ice  and  snow,  if  its  vapor  pressure  exceeds  that  of  the  air 
in  contact  with  it — and  it  will  follow  that  when  the  vapor  pres- 
sure of  the  air,  at  its  reduced  temperature,  is  greater  than  that 
of  the  vapor  of  the  ice  or  snow,  or  the  cooling  brine,  moisture 
will  be  deposited  from  the  air  upon  the  grid,  or  in  the  brine, 
the  density  of  the  brine  solution  being  lowered  in  consequence. 

The  quantity  of  water  per  cubic  foot  of  dry  air,  when  the  air 
is  saturated,  varies  from  0.000079  pound  at  o  degrees  F.,  up  to 
0.0368  pound  at  212  degrees  F.,  and  at  ordinary  barometric  pres- 
sure. With  air  that  is  to  be  cooled  from  70  to  15  degrees  F.,  and 
deprived  of  its  moisture,  it  is  necessary  to  first  abstract  the  heat 
carried  by  the  air  itself,  and  then  to  abstract  that  carried  as 
latent  heat  by  the  vapor.  The  two  operations  go  on  together, 
but  the  calculation  is  made  separately.  Thus  the  air  has  to  be 
cooled  55  degrees,  so  that  each  pound  of  air  must  be  deprived 
of  11  units,  and  each  cubic  foot  of  0.88  unit,  or  880  units  per 


METHODS    OF    COOLING    THE    AIR.  33 

1,000  cubic  feet.  If  we  take  the  vapor  saturation  of  the  air  as 
72  percent,  we  find  that  the  air  will  contain  0.0009  pound  per 
cubic  foot,  or  0.9  pound  per  1,000  cubic  feet,  and  this  will  mean, 
approximately,  that  900  heat  units  have  to  be  abstracted,  in  order 
that  the  vapor  may  assume  the  liquid  condition  and  be  deposited. 
If  it  is  formed  into  ice  or  snow,  as  usually  happens,  when  the 
moisture  is  deposited  on  the  grid,  the  latent  heat  of  the  liquid 
must  also  be  abstracted,  a  further  128  units,  or  a  total  of  1,908 
units  per  1,000  cubic  feet  of  the  air  to  be  cooled. 

The  above  figures  are  given  to  enable  marine  engineers  to  see 
how  the  calculations  are  made,  and  how  important  is  the  ques- 
tion of  the  vapor  in  the  air.  The  latter  is  changing  from  hour 
to  hour,  especially  when  a  ship  is  changing  her  latitude  somewhat 
rapidly,  and  therefore  any  calculations  that  are  made  should  be 
on  the  basis  of  the  worst  conditions  to  be  met.  If  the  air  is 
not  properly  dried,  some  vapor  will  pass  into  the  cold  chamber, 
and  will  there  be  deposited  upon  the  cold  surfaces  of  the  produce. 
Hence  sufficient  refrigerating  power  should  be  provided  to  extract 
the  largest  quantity  of  moisture  that  will  be  encountered. 

METHODS  OF  COOLING  THE  AIR. 

There  are  three  methods  employed,  though  only  two  of  them 
are  applicable  to  the  general  run  of  ship  work.  The  air  may  be 
caused  to  pass  over  the  surface  of  brine  that  has  been  cooled  to 
a  low  temperature;  it  may  be  caused  to  pass  over  the  surface 
of  a  grid  in  which  either  brine  or  the  refrigerant  is  circulating; 
or  again,  may  be  cooled  by  compression  and  expansion. 

The  first  method  is  the  most  economical,  and  is  largely  em- 
ployed in  cold  stores  on  shore.  The  usual  arrangement  includes 
cooling  the  brine  in  a  tank  through  which  the  refrigerant  is  cir- 
culating. It  is  then  carried  to  a  point  where  it  can  conveniently 
be  interposed  in  the  path  of  the  air.  At  this  point  a  battery  of 
galvanized  corrugated  iron  plates  is  fixed,  the  plates  being  hung 


34  COLD   STORAGE  ON   BOARD   SHIP. 

vertically.  The  brine  is  made  to  trickle  down  over  the  plates 
into  a  trough  below,  from  which  it  is  pumped  back  to  the  evap- 
orating brine  tank.  The  air,  which  has  done  its  work  in  the 
cold  store,  or  which  is  brought  fresh  from  the  outer  atmosphere, 
is  forced  between  the  plates  of  the  battery  by  a  fan.  In  passing 
between  them  it  is  cooled,  and  its  moisture  and  other  substances 
that  are  not  wanted  are  deposited  in  the  brine,  the  air  then 
passing  on  to  the  cold  chambers.  With  this  arrangement,  the 
brine  is  diluted  by  the  water  taken  from  the  air,  and  has  to  be 
subjected  after  a  time  to  a  process  of  partial  evaporation;  it  is 
boiled  in  a  pan  having  a  steam  jacket  until  its  density  is  restored 
to  the  proper  figure. 

In  the  next  plan  a  grid  of  pipes,  somewhat  similar  to  those 
that  have  been  described  for  cooling  the  cold  chambers  them- 
selves, is  placed  in  any  convenient  position  where  the  air  can  be 
forced  through  it  on  its  way  to  the  chamber.  The  air  with  ship 
work  is  taken  usually  from  the  atmosphere,  in  the  first  instance, 
by  means  of  a  shaft  leading  from  the  fan  chamber  to  a  sufficient 
height  above  the  upper  deck  to  insure  its  being  free  from  stoke- 
hold odors,  grease,  etc.  In  many  cases,  however,  the  same  air 
is  used  over  and  over  again,  being  passed  around  through  the 
fan  and  over  the  grid,  after  it  has  passed  out  of  the  chamber. 

The  fan  chamber  leads  directly  to  the  cooling  grid,  and  is  also 
connected  to  the  exit  ducts  of  the  cold  chamber,  the  engineer 
being  able  to  arrange  the  air  as  he  finds  best,  being  guided  in 
that  by  the  condition  of  the  produce.  He  also  has  it  in  his  power 
to  work  directly  from  the  atmosphere,  without  cooling  the  air 
at  all,  where  the  conditions  warrant  his  doing  so,  the  air  being 
simply  taken  in  from  the  atmosphere  and  expelled  to  the  atmo- 
sphere again.  The  cooling  grid  is  made  in  sections,  each  section 
being  connected  to  a  header,  where  valves  are  arranged,  so  that 
any  section  can  be  put  into  service  or  cut  out  at  will,  and  the 
refrigerant,  or  the  brine,  circulates  through  the  grid  according 
to  the  requirements  of  the  chamber.    In  hot  climates  the  engineer 


METHODS    OF    COOLING    THE    AIR. 


35 


may  have  perhaps  all  the  sections  in  service,  while  as  the  ship 
passes  into  colder  latitudes  he  will  take  off  one  section  after 
another,  and  possibly  in  cold  weather  depend  entirely  upon  the 
atmosphere  for  parts  of  the  day. 

As  mentioned  above,  the  moisture  present  in  the  atmosphere 
has  a  very  important  bearing  upon  the  question,  whether  the  air 


Liquified  Gad  Outlet^ 


DIAGRAM    OF    WEST    EVAPORATIVE    CONDENSER. 


shall  be  used  over  and  over  again,  or  whether  fresh  air  shall  be 
admitted.  When  it  is  used  in  a  closed  circuit  the  quantity  of 
moisture  present  and  the  temperature  of  the  air  coming  from 
the  chamber  are  known,  and  therefore  the  quantity  of  cooling 
the  latter  requires;  but  when  fresh  air  is  admitted  from  the 
outside,  the  engineer  does  not  know,  without  testing,  what  its 
hygroscopic  condition  is,  and  how  much  cold  will  be  required. 


30  COLD   STORAGE   ON   BOARD   SHIP. 

Hence  it  is  simpler  to  use  the  same  air  continuously.  The  mois- 
ture that  is  present  in  the  air  condenses  on  the  outside  of  the 
pipes  of  the  grid,  and  is  then  frozen,  the  frozen  skin  acting  very 
much  as  the  trickling  brine  does  with  the  battery  of  plates.  When 
the  machine  is  stopped,  the  mass  of  ice  and  snow  melts  and  is 
collected  in  a  trough  provided  for  it  under  the  grid,  and  dis- 
posed of  in  the   usual  way. 

COOLING  THE   AIR  BY   COMPRESSION   AND   EXPANSION. 

This  method  was  employed  a  good  deal  in  the  early  days  of 
cold  storage,  especially  for  ship  work,  and  it  has  a  great  deal 
to  recommend  it,  even  now,  for  small  work,  such  as  the  cold 
store  for  ship's  provisions  in  a  small  ship.  For  large  work  it  is 
not  so  economical,  and  the  quantity  of  air  required  is  so  much 
larger,  as  is  also  the  apparatus  to  deal  with  it,  that  it  has  grad- 
ually fallen  into  disuse,  except  for  special  cases.  On  the  com- 
pressed air  system,  air  is  taken  from  the  atmosphere  in  the  first 
instance,  drawn  into  a  cylinder  which  performs  the  office  of 
pump  and  compressor,  and  is  there  compressed  by  the  action  of 
a  piston.  In  the  act  of  compression  heat  is  generated  in  the  air. 
Now,  it  would  be  fatal  to  the  utility  of  the  air  as  a  cooling  agent 
if  any  moisture  were  present.  Hence,  after  passing  through  the 
compressor,  the  hot  air  is  passed  through  a  cooling  and  drying 
apparatus,  where  the  heat  which  has  been  generated  by  compres- 
sion is  taken  out,  and  any  moisture  it  carried  is  deposited. 

There  are  several  forms  of  cooling  apparatus  for  air,  the  prin- 
ciple being  the  same  as  already  described  for  cooling  the  air 
going  into  the  cold  chamber,  but  there  is  no  brine  grid  available. 
One  plan  is  to  pass  the  air  through  a  cylinder  containing  a  num- 
ber of  small  glass  balls,  like  marbles,  over  which  a  thin  stream 
of  water  trickles.  The  air  enters  the  cylinder  at  the  bottom, 
and  the  water  trickles  down  from  the  top.  The  air  is  gradually 
cooled  as  it  passes  upwards,  and  as  it  cools  deposits  the  moisture 


COOLING    THE    MR    BY    COMPRESSION    AND    EXPANSION.  $J 

it  carries,  so  that  it  issues  at  the  top  of  the  cylinder  partially 


cooled,  and  fairly  dry.     The  principal   cooling  is  performed  in 


3§  COLD    STORAGE    ON    BOARD    SHIP. 

the  next  operation,  in  a  second  cylinder,  whose  piston  rod  is 
connected  through  its  own  crank  to  the  same  crank  shaft  as 
that  of  the  compressor  piston.  This  is  called  the  expansion  cyl- 
inder, and  performs  the  same  office  as  the  expansion  coils  where 
a  refrigerant  is  employed.  The  air  which  has  been  cooled  and 
dried  is  allowed  to  pass  into  the  expansion  cylinder  behind  the 
piston,  which  it  works,  expanding  in  the  process.  The  cranks 
of  the  two  pistons  are  set  at  right  angles  to  each  other,  so  that 
the  work  which  the  expanding  air  performs  on  the  expansion 
piston  assists  the  compressor  piston.  In  expanding,  the  air  is 
cooled,  and  as  air  or  any  other  gas  can  expand  only  if  it  has  the 
space,  and  can  obtain  the  necessary  quantity  of  heat  to  enable  it 
to  do  so,  it  abstracts  heat  from  surrounding  bodies  and  becomes 
itself  lowered  in  temperature.  The  corripression  stroke  of  the 
compressor  coincides  with  the  expansion  stroke  of  the  expansion 
cylinder,  and  at  the  suction  stroke  of  the  compressor,  the  piston 
of  the  expansion  cylinder  forces  the  cooled  air  out  to  the  cold 
chamber,  or  wherever  it  is  to  go. 

The  cooled  air  is  employed  only  to  dilute  the  air  of  the  cold 
chamber,  so  that  the  temperature  of  the  latter  is  carried  at  what- 
ever figure  may  be  desired.  The  calculation  for  the  quantity  of 
air  to  be  cooled,  and  the  temperature  at  which  it  shall  be  forced 
into  the  cold  chamber,  is  simple.  Each  cubic  foot  of  the  cold 
air  will  absorb  a  certain  number  of  heat  units  while  its  tempera- 
ture is  being  raised  to  that  of  the  air  in  the  cold  chamber,  the 
temperature  of  the  latter  being  lowered  in  the  process;  but  it 
must  be  remembered  that  as  the  entering  air  rises  in  temperature, 
it  also  increases  in  volume,  and  the  cooling  effect  of  a  cubic  foot 
of  air,  at   each   succeeding  temperature,   becomes  less   and  less. 

In  practice  the  average  is  taken,  through  the  range  of  tem- 
perature. The  air  after  expansion  may  be  at  as  low  a  tempera- 
ture as  —85  degrees  P.  Some  makers  of  compressed  air  refrig- 
erating apparatus  claim  to  reduce  it  to  —100  degrees  F.  Taking 
it  at  —85   degrees   F.,   and   taking   the   mean   between   this  and 


LEADING    THE   COOLED    AIR    INTO    THE    COLD    CHAMBER. 


39 


the  temperature  at  which  the  cold  chamber  is  to  be  held,  say 
15  degrees  F.,  or  a  difference  of  50  degrees,  every  100  cubic  feet 
will  absorb  80  heat  units. 


LEADING  THE   COOLED   AIR   INTO  THE  COLD   CHAMBER. 

There   is  one  method   of  accomplishing  this   in   all   cases — by 
wooden  ducts  connecting  the  cooling  chamber  with  the  air  cham- 


ENOCK    iJ^-TON    INCLOSED    TYPE    MOTOR-DRIVEN    MACHINE. 


ber.  These  may  be  very  large,  where  the  air  is  cooled  merely  by 
the  aid  of  a  refrigerant — large  enough  for  a  man  to  walk  in — ■ 
and  will  contain  ports  opening  into  the  cold  chamber,  fixed  in 
positions  where  their  opening  will  direct  the  current  of  air  on 


40  COLD    STORAGE   ON   BOARD   SHIP. 

to  and  over  the  surface  of  the  produce  to  be  cooled.  The  manipu- 
lation of  the  ports  for  regulating  the  air  furnishes  one  reason 
for  making  the  ducts  large.  Another  and  perhaps  more  important 
reason  is  the  lessening  of  friction,  and  of  power  expended.  Air, 
like  brine  and  other  fluids,  rubs  on  the  surface  of  the  pipe  or 
duct  through  which  it  is  passing,  and  in  rubbing  sets  up  friction 
in  proportion  to  the  total  rubbing  surface,  and  to  the  square 
of  the  velocity  at  which  it  is  traveling.  Increasing  the  size  of 
the  ducts  adds  to  the  rubbing  surface  for  a  given  length,  but  it 
also  decreases  the  velocity  of  the  air,  and  the  gain  by  the  latter 
is  very  much  greater  than  the  loss  from  the  increased  rubbing 
surface.  Further,  where  produce  is  carried  it  is  very  important 
that  dust  and  other  objectionable  matter  shall  not  pass  into  the 
chamber,  and  this  can  be  assured  only  by  so  arranging  the  ducts 
that  they  can  be  kept  clean. 

The  velocity  at  which  the  air  passes  over  the  surface  of  the 
produce  has  an  important  bearing  upon  preservation.  Where  the 
temperature  does  not  matter,  so  long  as  it  is  below  a  certain 
figure,  an  air  current  at  a  high  velocity  will  make  no  difference, 
but  where  the  produce  has  to  be  maintained  at  a  certain  tempera- 
ture, it  has  a  great  effect.  When  cooling  by  air,  a  certain  quan- 
tity of  air  per  hour  must  be  passed  through  the  cold  chamber 
at  a  certain  temperature.  If  the  ducts  are  small,  the  air  must  pass 
through  them  at  a  higher  velocity  than  when  they  are  large, 
and  it  will  issue  into  the  cold  chamber  at  a  comparatively  high 
velocity,  with  the  result  that  the  produce  in  the  immediate  neigh- 
borhood of  the  inlet  ports  will  be  exposed  to  great — possibly 
injurious — cooling  effects,  while  that  at  a  distance  will  receive 
only  a  much  smaller  relative  effect.  It  is  the  same  thing  as  with 
the  drafts  from  which  we  catch  cold.  A  draft  is  merely  a  cur- 
rent of  air  passing  over  our  bodies  or  portions  of  them  at  a 
higher  velocity  than  is  good  for  us.  Every  cubic  inch  of  air  that 
passes  over  us  extracts  a  certain  number  of  heat  units  from  our 
bodies,  and  principally  from  the  part  over  which  it  passes.     If 


LEADING    THE   COOLED   AIR    INTO    THE  COLD   CHAMBER. 


41 


these  heat  units  are  taken  out  rapidly  the  temperature  of  the 
body  is  lowered,  particularly  at  the  spot  exposed  to  the  draft, 
and  congestion  results.     Similar  results  occur  with  produce. 

The  air  ducts  for  ship  work  are  practically  passages  surround- 
ing the  cold  chambers,  somewhat  on  the  lines  of  the  wing  pas- 
sages which  used  to  surround  the  old  wooden  ships  below  the 


CONDENSER    GIIAGE 


EVAPORATOR   GUAGE 


PATENT   SAFETY   VALV« 
IN    HERE 


REGULATOR 


EVAPORATOR    COIL 


COMPRESSOB 


PATENT    HOLLOW 
OIL   QLAND 


CONDENSEfi    COIL 


CONDENSER    CASING 


INSULATED    DIVISION    BETWEEN 
CONDENSER    A    EVAPORATOR 


SECTION    OF    HALL   CARBONIC-ACID   COMBINED    MACHINE. 


water  line,  along  which  a  man  could  walk  right  around  the  ship, 
to  stop  shot  holes,  leaks,  etc.  They  should  form  complete  cir- 
cuits for  the  passage  of  the  air  from  the  cooling  grid  and  back 
to  it  again,  with  doors  arranged  to  connect  them  to  the  cooling 
chamber  and  the  atmosphere.  With  compressec!  air  cooling,  even 
where  it  is  on  a  comparatively  large  scale,  there  is  not  much 
room  for  ducts,  both  because  warming  of  the  cooled  air  would 


4^  COLD  STORAGE  ON  BOARD  SHIP. 

taiee  piace  largely  in  the  ducts,  and  because  of  the  friction  men- 
tioned above.  The  air  cooled  by  compression  and  expansion  is 
led  to  the  cold  chamber  by  the  shortest  possible  route,  the  air 
duct  being  thoroughly  well  insulated.  The  use  of  the  large  air 
ducts  described  has  the  disadvantage  that  they  absorb  a  good 
deal  of  room  that  could  otherwise  be  filled  with  cargo,  but  the 
arrangement  is  much  the  best  for  certain  classes  of  produce,  such 
as   fruit. 

Where  the  cooled  air  system  is  employed  with  two  or  more 
substances,  having  odors  of  their  own,  the  ducts  leading  to  the 
different  chambers  must  not  be  allowed  to  connect  in  any  way. 
The  inlets  of  one  must  not  be  near  the  outlets  of  the  other,  and 
separate  cooling  apparatus  and  separate  fans  must  be  used,  if 
the  air  returns  from  the  chambers  to  the  cooling  plant.  The 
case  may  be  met  by  the  adoption  of  what  electricians  would  call 
the  parallel  system.  One  supply  of  air  could  be  employed,  and 
Dne  cooling  plant,  and  one  fan,  the  air  for  the  different  cham- 
bers being  directed  into  separate  ducts  and  then  discharged  into 
the  atmosphere  from  the  chambers ;  but  care  must  be  taken,  if 
this  plan  is  adopted,  that  the  air  which  passes  out  of  the  cham- 
bers does  not  get  to  the  shaft  from  which  the  inlet  air  is  taken. 


THE  DOORS   OF   COLD   CHAMBERS. 

The  doors  of  cold  chambers  are  very  important.  They  must 
be  constructed  on  the  same  lines  as  the  chambers  themselves. 
When  a  door  is  closed  it  must  form  part  of  the  wall  of  the  cham- 
ber into  which  it  fits,  in  the  sense  that  it  excludes  the  heat,  just 
as  much  as  the  chamber  wall  proper  does.  In  ship  work  the 
difficulty  is,  as  with  so  many  other  things,  to  find  room  for 
proper  doors.  The  thickness  of  the  doors  should  be  the  same 
as  that  of  the  walls;  and  as  far  as  practicable,  they  should  be 
built  in  the  same  way,  of  two  lots  of  matched  boarding,  facing 
each  other,  lined  with  waterproof  paper  on  their  inside  faces,  and 


THE  DOORS  OF  COLD  CHAMBER. 


43 


the  space  filled  with  an  insulating  material.    The  door  itself  also 
must  be  made  to  fit  air  tight  into  the  doorway.     There  must  be 


Cold  Water  Inlet 


Turbine  to  Operate  Agitator. 


■WKST   CONDENSER    OF    THE    SUBMERGED    TYPJj. 


no  cracks,  such  as  we  are  accustomed  to  in  the  doors  of  our 
living  rooms,  and  no  spaces  between  the  door  and  the  wall,  when 


44  COLD    STORAGE    ON    BOARD    SHIP. 

the  door  is  closed.  Further,  the  door  must  be  pressed  home 
firmly  when  closed,  and  the  fastening  be  such  that  it  cannot 
easily  work  loose,  even  in  a  heavy  seaway. 

When  the  cold  chamber  is  in  use  the  door  should  be  opened  as 
infrequently  as  possible,  and  then  closed  immediately;  for  every 
time  a  door  is  opened,  as  already  explained,  heat  is  admitted  to 
the  chamber,  which  means  more  work  for  the  machines.  On 
shore,  wherever  it  can  be  arranged,  double  doors  are  fixed,  the 
outer  being  closed  before  the  inner  is  opened,  so  that  only  the 
small  lobby  full  of  air  from  outside  is  admitted. 


HOW  THE  LOW  TEMPERATURE  OF  THE  BRINE  OR  REFRIGERANT  IS   PRO- 
DUCED. 

The  operation  of  one  method,  that  of  alternately  compressing 
air  and  allowing  it  to  expand,  has  been  described.  The  other 
method,  of  which  there  are  two  variations,  has  been  partly  indi- 
cated. A  refrigerant,  ammonia,  carbonic  acid  or  sulphurous  acid, 
these  solutions  lending  themselves  peculiarly  to  this  work,  is 
caused  to  assume  alternately  the  liquid  state,  and  the  gaseous 
state.  In  expanding  from  a  liquid  to  a  gas,  it  abstracts  heat  from 
the  brine,  the  air  of  the  chamber,  etc.,  as  has  been  shown.  To 
accomplish  this,  and  to  work  economically,  a  circuit  is  formed, 
consisting  of  the  compressor  or  its  equivalent,  as  will  be  de- 
scribed, the  condenser,  the  expansion  coils,  and  the  connecting 
pipes.  The  compressor  is  practically  a  pump.  After  the  refrig- 
erant has  done  its  work,  and  become  a  gas,  it  is  sucked  back 
into  the  compression  cylinder,  compressed,  and  then  forced  into 
the  condenser,  passing  thence  to  the  expansion  coils  and  back  to 
the  compressor. 

The  latter  consists  of  one  or  more  cylinders  in  which  pistons 
work,  very  much  on  the  lines  of  steam  cylinders,  but  with  cer- 
tain modifications.  There  are  one  or  more  suction  valves  to  each 
compressor,  and  one  or  more  delivery  calves.    The  cylinders  may 


HOW    THE   LOW    TEMPERATURE   IS    PRODUCED. 


4h 


be  either  single  or  double  acting.     If  single  acting,  gas  is  taken 
in  on  one   stroke  and  compressed  on  the   return  stroke,   some- 


thing on  the  lines  of  the  old  Cornish  single  acting  engine,  but 
with  the  operation  reversed.  When  double  acting,  gas  is  taken 
in  at  each  stroke,  and  compressed  at  each  stroke,  the  rear  of  the 


40  COLD   STORAGE  ON  BOARD  SHIP. 

piston  performing  the  office  of  suction,  while  the  front  com- 
presses. The  valves  are  all  of  one  type,  shaped  like  the  frustum 
of  a  cone,  seated  in  extensions  of  the  cylinder  covers  and  kept 
on  their  seats  by  spiral  springs,  which  allow  them  to  open  in- 
wards or  outwards,  as  the  pressure  is  reduced  or  increased  :uf- 
ficiently  to  allow  the  spring  to  operate  in  the  case  of  the  suction 
valve,  and  to  overcome  the  spring  in  the  case  of  the  delivery 
valve.  The  piston  also  is  slightly  different  from  the  ordinary 
steam  or  compressed  air  piston. 

Marine  engineers  are  well  acquainted  with  the  evils  of  clear- 
ance in  engine  cylinders.  With  compressors  used  for  refriger- 
ating apparatus  the  trouble  is  very  much  increased,  because  the 
small  quantity  of  the  gas  remaining  in  the  cylinder,  in  the  clear- 
ance space,  is  in  a  highly  compressed  form,  and  immediately  it 
is  released  by  the  return  of  the  piston,  expands,  occupying  the 
space  left  vacant,  and  introducing  a  pressure  against  the  ingress 
of  the  next  lot  of  gas,  thus  reducing  the  quantity  taken  in  on 
the  suction  stroke.  To  obviate  this,  nearly  all  compressors  are 
made  with  the  ends  of  the  cylinders  dome  shaped,  and  the  ends 
of  the  pistons  hemispherical,  or  as  nearly  so  as  they  can  be  made, 
so  that  they  run  very  close  up  to  the  cylinder  end.  One  firm  in 
the  United  Kingdom  uses  a  flat  cylinder  end,  a  flat  piston,  and 
provides  a  spring  which  is  compressed  as  the  piston  moves  up  to 
the  cylinder  end,  the  spring  taking  the  thrust,  keeping  the  piston 
away  from  the  end  of  the  cylinder,  and  helping  to  start  it  back 
on  the  return  stroke. 

The  De  La  Vergne  Company  of  New  York  employs  another 
method.  A  small  quantity  of  oil  is  injected  into  the  cylinder, 
shortly  before  the  end  of  the  stroke,  and  the  oil  and  gas  are 
ejected  together,  the  refrigerant  being  freed  from  the  oil  by  a 
separator  before  being  used  again.  The  delivery  valves  open 
automatically  when  the  pressure  inside  the  cylinder  on  the  com- 
pression side  of  the  piston  is  sufficient  to  overcome  the  tension 
of  the  spiral   spring,   and  close  immediately  when  the  pressure 


HOvV     THE    LOW     TEMPERATURE    IS     PRODUCED. 


47 


is  reduced  sufficiently  for  the  spring  to  overcome  it;  the  suction 
valve  doing  the  same,  in  the  reverse  direction. 


SUBMERGED    CONDENSER. 
a    AMMONIA    INLET.  C  WATER    INLET. 


b.  AMMONIA  OUTLET. 


d.    WATER   OUTLET. 


Compressors  for  refrigerating  machines  are  often  made  com- 
pound.   The  compression  is  completed  in  two  cylinders,  there 


40  COLD    STORACE    ON    BOARD    SHIP. 

being  sometimes  an  intercooler  between  the  two.  The  gas  Is 
compressed  to  a  certain  pressure  in  one  cylinder,  and  the  con\ 
plete  pressure  obtained  in  the  second.  It  is  the  reverse  operation 
to  that  of  a  compound  engine.  In  the  act  of  compression  the 
gas  is  made  to  take  up  a  smaller  volume,  and  becomes  heated, 
just  as  air  does  in  compression.  It  is  necessary  to  compress 
the  gas  in  order  to  enable  it  to  be  liquefied  with  a  reasonable  quan- 
tity of  cooling  water.  The  molecules  of  the  gas  are  brought 
closer  together,  and  are  then  more  ready  to  take  on  the  liquid 
form.  But  in  order  that  the  gas  may  become  a  liquid,  the  heat 
of  compression,  as  well  as  the  latent  heat  of  the  gas,  must  be 
removed.  Further,  as  it  becomes  heated  it  tends  to  expand,  and 
to  occupy  a  greater  space  than  it  would  otherwise  do,  and  than 
it  will  do  when  the  heat  is  removed.  It  is  for  this  reason  that 
the  intercooler,  where  compound  compression  rules,  is  so  valuable. 
By  removing  the  heat  of  compression  of  the  first  cylinder,  the 
volume  entering  the  second  cylinder  is  smaller  for  the  work  that 
is  to  be  accomplished.  Besides,  the  heat  generated  would  other- 
wise act  upon  the  cylinder  itself,  and  if  allowed  to  become  too 
great,  upon  the  valves. 

When  the  compression  cylinder  is  hot  the  gas  entering  at  the 
suction  stroke  is  heated  and  expands,  and  the  weight  that  is 
taken  in  at  each  stroke  is  lessened,  so  thai,  the  efficiency  of  the 
apparatus  is  thereby  reduced,  for  more  work  has  to  be  done  by 
the  compressor  for  the  same  refrigerating  effect.  There  are 
several  methods  of  dealing  with  this  matter.  One  has  already 
been  referred  to,  that  of  the  De  La  Vergne  Company.  The  oil 
which  is  injected  into  the  cylinder  to  fill  the  clearance  space  also 
cools  the  cylinder  itself,  by  absorbing  some  of  the  heat.  Another 
method  is  what  is  termed  the  "wet  compression."  A  small  quan- 
tity of  liquid  refrigerant  is  allowed  to  pass  into  the  compressor, 
with  the  gas.  On  its  entrance  into  the  cylinder,  it  expands  to  the 
gaseous  state,  absorbing  some  of  the  heat  of  the  cylinder  walls, 
etc.     One  objection  to  this  is  that  it  is  difficult  to  arrange   it 


THE    CONDENSER.  49 

properly,    and    its    effective    operation    must    depend    upon   the 
attendant. 

The  cooling  is  effected  in  the  expansion  coils  by  the  passage 
of  sufficient  liquid  refrigerant  into  them,  to  absorb  the  heat  that 
is  to  be  taken  away.  Any  additional  quantity  of  liquid  refriger- 
ant that  is  allowed  to  pass  through  lowers  the  efficiency  of  the 
machine,  as  it  has  to  be  handled  without  giving  back  any  useful 
result.  On  the  other  hand,  cooling  the  cylinder  by  the  aid  of 
the  refrigerant  adds  to  the  efficiency.  It  is  again  a  case  of  the 
balance  sheet.  Another  method  is  the  well-known  one  employed 
with  gas  engines,  of  circulating  cooling  water  in  a  cylinder 
jacket.  Double  acting  compressors  heat  more  than  single  acting, 
as  will  be  easily  understood,  and  for  that  reason  many  engineers 
prefer  single  acting  apparatus. 

THE  CONDENSER. 

The  condenser  for  refrigerating  apparatus  is  designed  to  per- 
form the  same  office  for  the  refrigerant  that  the  steam  condenser 
does  for  the  steam — to  convert  it  to  the  liquid  form.  Its  con- 
struction is  very  similar.  There  are  two  forms  of  condenser 
used  in  refrigerating  work,  the  submerged,  and  the  open.  In 
both  forms  the  hot  gas  passes  through  pipes,  over  which  cooling 
water  runs.  In  the  submerged  form,  the  pipes  are  usually  in 
coils,  in  a  circular  tank,  and  the  cooling  water  is  kept  contin- 
ually in  circulation  over  its  surface.  It  is  practically  a  surface 
condenser.  In  the  open  type,  the  pipes  are  usually  made  in  grids, 
the  cooling  water  being  allowed  to  trickle  down  over  them. 
The  cooling  effect  is  largely  due,  with  the  open  type,  to  evapo- 
ration. In  fact  they  are  generally  known  as  evaporative  con- 
densers, and  are  preferred  on  shore,  wherever  they  can  be  em- 
ployed, on  account  of  their  higher  efficiency  and  the  smaller 
quantity  of  cooling  water  required.  A  small  portion  of  the  water 
which  trickles  down  over  the  pipes  is  evaporated,  carrying  off 


50  COLD    STORAGE    ON    BOARD    SHIP. 

with  it,  approximately,  10,000  heat  units  for  every  gallon  evapo- 
rated, where  a  gallon  of  water  passing  over  the  pipes  in  liquid 
form  carries  off  only  from  100  to  200  units. 

Condensers  used  for  refrigerating  apparatus  are  slightly  dif- 
ferent from  those  used  for  steam,  mainly  because  it  is  so  impor- 
tant that  there  shall  be  no  leakage  of  the  refrigerant.  There  are 
no  joints  in  the  pipes  inside  the  submerged  condenser.  The  coil 
is  made  in  one  long  length,  welded  sometimes  by  electricity, 
sometimes  by  special  lap  welds,  but  never  jointed.  If  joints  are 
necessary,  and  where  they  are  necessary,  the  pipe  is  brought  out 
of  the  tank,  and  the  joint  made  there.  With  open  type  con- 
densers the  pipes  are  all  fitted  into  headers  at  each  end.  In  either 
case,  any  kind  of  water  may  be  used,  provided  that  no  crust  is 
allowed  to  form  on  the  outside  of  the  pipe  by  the  salts  contained 
in  the  water.  Sea  water  may  be  used,  provided  that  this  point 
is  attended  to.  If  a  deposit  is  formed,  a  certain  resistance  is  set 
up  between  the  refrigerant  inside  and  the  cooling  water  outside, 
apart  from  and  in  addition  to  that  of  the  pipe  itself,  with  the 
result  that  the  cooling  water  has  not  its  proper  effect,  and  more 
has  to  be  used. 

All  refrigerating  condensers  are  worked  on  the  counter  cur- 
rent principle,  the  cooling  water  and  the  hot  gas  circulating  in 
opposite  directions.  The  water  usually  passes  from  below  up- 
wards, while  the  hot  gas  enters  above  and  passes  downwards. 
The  hottest  gas  meets  the  hottest  water,  and  is  partially  cooled, 
meeting  colder  and  colder  water  as  it  passes  downwards,  and  is 
itself  becoming  colder  and  colder,  till  at  the  bottom  it  meets  the 
fresh  and  coldest  water.  The  liquid  refrigerant  which  is  formed 
runs  out  at  the  bottom  to  a  receiver,  where  one  is  used,  and 
usually  through  an  oil  separator,  to  the  evaporator  coils. 

Obviously  the  submerged  condenser  is  the  one  adapted  for  ship 
work,  but  there  are  cases  where  the  open  condenser  would  do 
good  work.  It  must  be  remembered  that  a  current  of  air  is 
of  great  service,  especially  when  the  air  is  warm  and  dry,  as  it 


THE    CONDENSER. 


51 


very  materially  assists  evaporation,  and  cooling  with  it.  In  the 
Savoy  Hotel  in  London  the  cooling  water  for  the  refrigeration 
condenser  is  itself  cooled  by  means  of  the  equivalent  of  a  cooling 


Nouons  aaivM 


tower,  fixed  in  the  shaft  which  carries  off  the  vitiated  air  from 
the  chimneys,  stoke  hold,  etc.  Galvanized  iron  wire  mats  are 
hung  in  the  shaft,  and  a  fan  at  the  bottom  directs  the  air  through 


52  COLD    STORAGE   ON    BOARD    SHIP. 

them,  while  the  water  to  be  cooled  trickles  down  over  them. 
Something  similar  to  this  might  be  arranged  on  board  ship  for 
the  refrigerating  condenser,  the  coils  in  which  the  hot  gas  passes 
taking  the  place  of  the  wire  mats,  and  some  of  the  hot  air  from 
the  ship,  if  not  too  much  saturated  with  moisture,  being  driven 
over  it. 

As  already  explained,  there  are  three  substances  employed  as 
refrigerants,  ammonia,  carbonic  acid  and  sulphurous  acid.  All 
are  worked  upon  the  same  lines,  but  the  sizes  of  the  apparatus 
and  the  pressures  at  which  they  are  worked  vary  considerably. 
In  addition  there  is  another  process  employed  with  ammonia, 
known  as  the  absorption  process,  which,  after  varying  fortunes, 
appears  to  be  coming  to  the  front  again,  even  for  ship  work.  It 
is  described  below.  The  different  agents  have  different  latent 
heats,  and  therefore  different  refrigerating  capacities.  The  capac- 
ity of  any  refrigerant  depends  upon  its  latent  heat,  that  is,  its 
ability  to  absorb  heat  in  passing  from  the  liquid  to  the  gaseous 
state.  This  quantity  is  usually  stated  in  British  thermal  units  per 
pound  of  the  refrigerant,  just  as  that  of  steam  is. 

Perfectly  anhydrous  (water  free)  ammonia  has  a  latent  heat 
of  555-5  units  per  pound  at  zero  F.,  the  pressure  being  30  pounds 
per  square  inch.  Carbonic  acid  at  the  same  temperature,  but  at 
a  pressure  of  310  pounds  per  square  inch,  has  a  latent  heat  of 
123.2  units  per  pound;  while  sulphurous  acid  at  the  same  tem- 
perature has  a  latent  heat  of  171.2  units.  The  latent  heat  varies 
with  the  temperature  and  pressure.  The  refrigerants  employed 
have  all  their  critical  temperatures,  above  which  they  will  not 
assume  the  liquid  state,  no  matter  to  what  pressure  they  are 
subjected.  Apart  from  that,  the  temperature  of  the  refrigerant 
varies  with  the  pressure,  just  as  in  the  case  of  steam.  But  as 
the  temperature  and  pressure  increase  the  latent  heat  decreases. 
Thus,  at  a  temperature  of  — 40  degrees  F.,  and  an  absolute  pres- 
sure of  10  pounds  per  square  inch,  the  latent  heat  of  ammonia  is 
579  units  per  pound,  while  at  a  pressure  of  42  pounds  per  square 


THE   CONDENSER. 


53 


inch,  and  a  temperature  of  15  degrees  F.,  its  latent  heat  is  only 
546  units  per  pound.  Similarly  carbonic  acid,  at  a  temperature 
of  — 22  degrees  F.,  and  a  pressure  of  195  pounds  per  square  inch, 


•'automatic"  3-horsepower  machine  with  ELECTRIC   driv«. 


has  a  latent  heat  of  136  units  per  pound,  while  at  a  pressure  of  380 
pounds  per  square  inch,  and  a  temperature  of  14  degrees  F.,  its 
latent  heat  is  only  115  units  per  pound. 


54  COLD    STORAGE    ON    BOARD    SHIP. 

It  will  be  observed  that  the  latent  heats  are  expressed  in  terms 
of  pounds  of  the  different  substances,  because  all  of  these  figures 
arising  out  of  heat  units  are  naturally  referred  to  weight,  since 
the  heat  unit  goes  by  weight.  But  in  refrigerating  apparatus  it 
is  volumes  that  are  dealt  with.  A  certain  volume  of  the  gas 
which  has  done  its  work  in  the  expansion  coils  is  dealt  with  in 
the  compressor  at  each  stroke.  Hence  it  is  more  important  to 
know  the  latent  heats  of  the  different  refrigerants  per  cubic 
foot,  and  then  it  will  be  seen  that  the  apparent  advantage  of 
ammonia  in  the  matter  of  latent  heat  is  not  maintained.  One 
pound  of  ammonia  measures  10.33  cubic  feet  at  — 4  degrees  F., 
while  one  pound  of  carbonic  acid,  at  the  same  temperature,  meas- 
ures only  0.312  cubic  foot,  and  sulphurous  acid  8.06  cubic  feet. 
Hence  the  latent  heat  of  a  cubic  foot  of  ammonia  at  — 4  degrees 
is  56  units,  while  that  of  a  cubic  foot  of  carbonic  acid  is  about 
400  units  at  the  same  temperature,  so  that  carbonic  acid  has  the 
advantage. 

In  practice  there  are  other  matters  to  take  into  consideration, 
which  bring  the  efficiencies  of  the  three  agents  to  about  the  same 
value.  Carbonic  acid  is  supposed  to  be  not  so  efficient  in  hot 
climates  as  ammonia,  but  very  good  work  is  being  done  with  it 
in  India  and  in  ships  trading  to  the  tropics.  In  fact,  it  is  the 
refrigerant  most  commonly  employed  for  ship  work.  Its  critical 
temperature  is  88.43  degrees  F.  It  was  supposed  for  some  time 
that  it  would  not  work  where  water  of  high  temperature  only 
was  obtainable.     This  has  however  been  fully  disproved. 

It  will  be  noticed  that  the  pressures  at  which  the  different 
refrigerants  are  worked  vary  considerably.  The  working  pres- 
sures are — for  ammonia,  in  the  neighborhood  of  40  pounds  per 
square  inch  in  the  evaporating  coils,  and  120  to  170  pounds  in 
the  condenser;  with  carbonic  acid,  380  pounds  per  square  inch  in 
the  evaporator,  and  800  to  900,  sometimes  going  very  much 
higher,  in  the  condenser;  while  with  sulphurous  acid  the  evap- 
orator pressures  are  in  the  neighborhood  of  14  pounds,  and  the 


THE   CONDENSER. 


55 


condenser  pressures  about  45  pounds.  It  will  be  seen  from  the 
above  how  the  various  claims  set  up  by  the  makers  of  different 
apparatus,  using  the  different  agents,  are  obtained. 


AIR 

CI.    AIR    INLET. 
b.    AIR    OUTLET. 
C.     AMMONIA     INLET. 


d.  AMMONIA    OUTLET. 

e.  BRINE    INLET. 

f.  BRINE     OUTLET. 


The  high  pressure  necessary  with  carbonic  acid  is  easily  pro- 
vided for,  by  mechanical  construction.  In  the  United  Kingdom, 
Messrs.  J.  &  E.  Hall,  of  London,  who  have  made  a  specialty  of 


56  COED   STORAGE  ON   BOARD  SHIP. 

carbonic  acid  machinery,  construct  the  compressor  cylinder  out 
of  a  solid  ingot  of  special  steel,  the  space  for  the  piston,  the 
valves,  etc.,  being  bored  out  with  special  tools  at  one  setting. 
Meanwhile  the  high  pressure  and  small  quantity  of  refrigerant 
enables  smaller  compressors  to  be  employed,  a  matter  of  con- 
siderable advantage  in  ship  work.  The  makers  of  sulphurous 
acid  apparatus  claim,  on  the  other  hand,  that  their  low  pressures 
enable  them  to  work  with  weaker  apparatus.  In  practice  am- 
monia and  sulphurous  acid  cylinders  are  of  about  the  same  size. 
The  condenser  pressure  is  really  the  delivery  pressure  of  the 
compressor,  while  the  evaporator  pressure  is  the  suction  or  back 
pressure  of  the  compressor.  The  evaporator  pressure  corresponds 
to  the  back  pressure  of  a  steam  engine,  but  in  contradistinction  to 
the  steam  engine,  it  is  an  advantage  to  have  the  back  pressure 
comparatively  high,  because  it  means  that  the  gas  weighs  more 
to  the  cubic  foot,  and  therefore  more  is  taken  in  at  each  suction 
stroke.  The  work  of  cooling  is  done  mainly  by  the  conversion 
of  the  liquid  into  gas.  Some  heat  -is  carried  off  by  the  refrigerant, 
after  it  has  become  a  gas,  but  this  is  a  small  quantity,  and 
though  the  cooling  effect  of  each  cubic  foot  of  the  refrigerant, 
when  in  the  gaseous  state,  is  reduced  by  the  higher  pressure  and 
temperature,  there  is  the  gain  by  the  greater  density  of  the  gas, 
as  explained.  As  before,  it  is  a  question  of  a  balance  sheet. 
There  is  a  critical  value  beyond  which  it  is  not  economical  to 
increase  the  back  pressure,  because  the  loss  of  cooling  is  greater 
than  the  gain  by  increased   density. 

LUBRICATION    AND    STUFFING    BOXES    OF    COMPRESSORS. 

The  lubrication  of  compressors  is  an  important  matter,  just 
as  is  that  of  steam  cylinders.  For  carbonic  acid  machines  gly- 
cerine is  employed,  and  for  ammonia  machines  a  special  lubri- 
cant that  will  not  saponify,  in  combination  with  the  ammonia 
itself,  as  nearly  all  of  the  ordinary  lubricants  are  said  to  do. 


LUBRICATION     AND    STUFFING    BOXES    OF    COMPRESSORS.  57 

With  sulphurous  acid,  the  substance  itself  forms  a  good  lubri- 
cator when  pure,  but  great  care  must  be  taken  that  water  is  not 
allowed  to  penetrate  to  the  cylinder,  as  then  sulphuric  acid  may  be 
formed,  with  attendant  troubles.  Whatever  lubricant  is  em- 
ployed other  than  the  refrigerant  itself  a  small  quantity  will  mix 
with  the  refrigerant  and  has  to  be  removed  before  the  latter 
can  be  again  used.  For  this  reason  all  ammonia  and  carbonic 
acid  apparatus  is  fitted  with  rectifiers,  or  oil  separators,  to  remove 
the  oil  before  the  refrigerant  passes  to  the  condenser. 

The  separator  consists  of  an  iron  cylinder  having  a  water 
jacket,  so  that  its  temperature  is  maintained  lower  than  that  of 
the  compressed  gas  it  has  to  deal  with.  In  the  cylinder  are  fixed 
baffles  of  various  forms,  which  arrest  the  particles  of  oil,  and 
allow  the  purified  gas  to  pass  on.  It  is  doubtful  if  the  whole 
of  the  oil  is  removed  by  any  of  the  separators,  but  a  sufficient 
quantity  is  taken  out  to  permit  the  apparatus  to  continue  to  run. 

The  matter  of  the  stuffing  boxes  is  another  very  important  one. 
There  are  two  kinds  of  leakage  to  be  guarded  against,  that  of 
the  refrigerant  out  of  the  cylinder,  which  is  similar  to  a  leakage 
of  steam  from  a  steam  cylinder,  with  the  addition  that  the  loss 
has  to  be  made  up,  and  that  of  air  and  moisture  from  outside 
into  the  cylinder.  Every  cubic  foot  of  air  that  enters  the  cyl- 
inder dilutes  the  refrigerant  to  that  extent,  thereby  lowering  the 
efficiency  of  the  apparatus,  since  a  part  of  the  power  will  be  taken 
up  in  compressing  air  instead  of  the  refrigerant  gas,  and  the  air 
will  also  occupy  some  of  the  useful  space  in  the  condenser  and 
the  evaporator,  and  may  lead  to  air  troubles.  With  ammonia, 
also,  the  refrigerant  has  such  a  strong  affinity  for  water  that  any 
leakage  of  moisture  into  the  cylinder  may  cause  a  serious  loss 
of  efficiency. 

For  these  reasons  the  stuffing  boxes  of  the  piston  rods  of  the 
compression  cylinders  are  made  especially  long,  and  are  packed 
with  especial  care.  Usually  the  packing  is  in  two  sections,  a  dis- 
tance piece  separating  the  two,  and  the  packing  itself  soaked  in 


58  COLD   STORAGE   ON    BOARD   SHIP. 

oil.  In  some  forms  of  apparatus  there  is  a  small  reservoir  of  oil 
attached  to  the  stuffing  box,  and  the  oil  is  kept  by  various  devices 
under  the  same  pressure  as  the  condenser.  Messrs.  J.  &  E.  Hall 
have  a  small  auxiliary  cylinder,  the  piston  of  which  is  exposed, 
by  means  of  a  small  connecting  pipe,  to  the  condenser  pressure,. 
the  piston  itself  acting  upon  a  body  of  glycerine  held  in  the  other 
part  of  the  cylinder,  while  the  cylinder  communicates  by  another 
small  passage  with  the  stuffing  box. 

ABSORPTION   MACHINES. 

At  the  present  time  ammonia  is  the  only  refrigerant  that  is 
employed  with  the  absorption  process.  The  absorption  apparatus 
takes  the  place  of  the  compressor  and  its  immediate  accessories 
only.  There  is  the  same  circuit,  with  modifications  that  will  be 
mentioned,  but  the  modifications  are  confined  to  parts  of  the 
absorption  plant  itself.  There  are  the  same  condenser  and  evapo- 
rator, as  with  the  compression  system,  and  the  same  figures  for 
lengths  and  sizes  of  pipes  for  the  condenser  and  evaporator  will 
rule.  Also,  brine  is  used  with  the  absorption  system,  as  with  the 
compression  system;  and,  finally,  though  it  is  called  an  absorp- 
tion system  and  works  by  the  alternate  absorption  and  expulsion 
of  ammonia  it  is  really  a  compression  system,  the  compression 
being  produced  by  the  continuous  delivery  of  the  ammonia  from 
solution.  It  is  also  the  same  anhydrous  ammonia  that  is  em- 
ployed to  charge  the  machine  when  starting  up. 

The  operation  of  the  apparatus  depends  upon  the  ability  of 
water  to  dissolve  ammonia,  whether  in  the  gaseous  or  the  liquid 
condition.  This  capacity  for  dissolving  or  absorbing  ammonia 
varies  with  the  temperature  of  the  water,  decreasing  as  the  tem- 
perature rises  and  vice  versa.  Further,  it  will  be  remembered 
that,  when  a  gas  is  dissolved  in  a  liquid,  it  assumes  the  liquid 
form,  giving  up  its  gaseous  latent  heat  to  the  liquid. 

In  the  modern  absorption  apparatus  there  are  two  principal 
vessels,  called  the  generator  and  the  absorber.     The  generator 


ABSORPTION   MACHINES. 


59 


contains  an  aqueous  solution  of  ammonia,  which  is  kept  as  strong 
as  possible,  and  to  which  heat  is  applied,  usually  by  the  aid  of 


steam  circulating  in  pipes.  The  absorber  receives  the  gas  which 
has  done  its  work  in  the  evaporator.  The  generator  corresponds 
to  the  delivery  side  of  the  compressor,  and  the  absorber  to  the 


60  COLD    STORAGE   ON    BOARD    SHIP. 

suction  side.  The  heat  applied  to  the  generator,  by  raising  the 
temperature  of  the  water,  obliges  it  to  expel  some  of  the  am- 
monia it  holds  in  solution,  the  gas  passing  from  it  to  the  con- 
denser, after  it  has  been  subject  to  certain  other  processes.  The 
continual  expulsion  of  the  ammonia  gas  from  the  generator  raises 
the  pressure  behind  the  gas  that  is  entering  the  condenser,  just 
as.  the  continuous  generation  of  steam  in  a  boiler  raises  the  pres- 
sure in  the  steam  chest  and  the  pipes  leading  from  it.  Suf- 
ficient compression  is  produced  for  the  gas  to  be  liquefied  in  the 
condenser,  as  in  the  compression  system. 

The  liquid  in  the  absorber  is  maintained  at  as  low  a  satura- 
tion and  as  low  a  temperature  as  possible,  in  order  that  it  may 
be  able  to  absorb  all  of  the  gas  that  comes  over  from  the  evapo- 
rator. In  dissolving,  the  gas  liberates  the  latent  heat  it  pos- 
sessed as  a  gas,  raising  the  temperature  of  the  solution.  Now  it 
will  be  evident  that  unless  some  arrangement  is  made  for  carry- 
ing the  ammonia  over  to  the  generator  as  it  is  received,  the  latter 
will  soon  run  down.  In  one  form  of  apparatus  that  was  on  the 
market  a  short  time  since,  the  two  vessels,  which  were  in  the 
form  of  cylinders,  were  made  to  perform  the  offices  of  generator 
and  absorber  alternately,  the  change  being  carried  out  by  turn- 
ing valves  arranged  for  the  purpose,  after  a  certain  number  of 
hours'  work.  This  arrangement  has  now  been  abandoned,  and 
the  work  goes  on  continuously,  without  any  change  of  vessels. 

The  absorber  is  cooled  by  water  circulating  in  pipes  in  the 
cylinder.  Further  than  this,  some  of  the  heat  that  is  not  wanted 
in  the  absorber  is  delivered  to  the  generator  in  an  apparatus 
called  the  exchanger,  which  is  an  accessory  to  every  absorption 
apparatus.  The  continual  expulsion  of  the  gas  by  the  generator 
has  a  secondary  effect,  in  lowering  the  specific  gravity  of  the 
liquid.  Hence  the  liquid  from  which  the  gas  has  been  driven 
off  tends  to  fall  to  the  bottom  of  the  cylinder  of  which  the  gen- 
erator is  composed.  In  the  absorber  the  same  process  is  going 
forward,  but  in  the  opposite  direction,  so  pipes  are  arranged  to 


ABSORPTION   MACHINES. 


Gl 


carry  off  the  weak  liquid  from  the  generator  to  the  absorber, 
and  to  carry  the  stronger  liquid  from  the  absorber  to  the  gen- 


erator.   These  two  liquids  pass  through  the  exchanger  in  sepa- 
rate pipes,  arranged  so  that  the  hot  liquid  from  the  generator, 


62  COLD    STORAGE    ON    BOARD    SHIP. 

which  is  on  its  way  to  the  absorber,  shall  deliver  its  heat,  or  as 
much  of  it  as  possible,  to  the  liquid  that  is  on  its  way  from  the 
absorber  to  the  generator.  The  exchanger,  in  some  forms,  in- 
cludes also  some  pipes  through  which  cooling  water  passes,  so 
that  the  weak  liquid  may  enter  the  absorber  at  as  low  a  tempera- 
ture as  possible.  But  the  above  does  not  complete  the  tale  of 
the  apparatus  required. 

Marine  engineers  are  familiar  with  the  fact  that  when  steam 
is  generated,  small  globules  of  water  pass  over  with  the  steam, 
and  give  more  or  less  trouble  after,  if  not  disposed  of.  The 
same  thing  happens  with  the  ammonia — some  water  passes  over 
with  the  gas,  in  various  forms,  and  must  be  got  rid  of,  for  the 
reasons  already  given.  For  this  there  are  two  pieces  of  appa- 
ratus, usually  also  in  the  form  of  cylinders,  called  the  analyzer 
and  the  rectifier.  The  analyzer  sometimes  forms  part  of  the 
generator.  Both  pieces  of  apparatus  are  designed  to  precipitate 
the  water,  however  carried,  and  to  return  it  to  the  generator. 

The  analyzer  consists  of  baffles  of  various  forms,  over  which 
the  gas  is  made  to  pass  on  its  way  from  the  generator,  and 
which  tend  to  catch  any  globules  of  water  held  mechanically  by 
the  gas,  these  running  back  into  the  water  from  which  the  gas 
was  expelled.  In  some  apparatus,  the  rich  liquid  coming  from 
the  absorber  is  made  to  run  over  different  obstacles  on  its  way 
into  the  generator,  meeting  the  hot  gas  that  is  coming  away, 
another  exchange  taking  place,  the  liquid  taking  up  the  water 
from  the  gas,  and  having  its  temperature  increased.  The  rectifier 
usually  consists  of  another  cylinder,,  in  which  the  gas  is  cooled 
before  passing  to  the  condenser.  The  temperature  of  the  gaseous 
mixture  is  lowered  to  a  point  below  that  at  which  the  water 
held  in  suspension  can  exist  as  vapor,  the  water  being  then  con- 
densed and  running  back  to  the  generator. 

In  the  latest  form  of  apparatus  made  in  the  United  Kingdom, 
trv    Messrs.    Ransome    and    Rapier,*    the    apparatus    consists    of 


*32  Victoria   Street,  London,  W.,   England. 


CIRCULATING    PUMPS.  63 

several  cylinders,  mounted  horizontally,  partly  side  by  side,  and 
partly  one  above  the  other,  the  condenser  forming  one  of  them. 
One  lot  of  cooling  water  answers  for  the  whole  apparatus,  pass- 
ing through  the  different  cylinders  in  succession.  There  is  a 
small  pump  employed  to  carry  the  ammonia  liquid  from  the 
absorber  to  the  generator,  and  there  will  be  a  water  pump  re- 
quired, where  city  water  under  pressure  is  not  employed. 

CIRCULATING   PUMPS. 

Two  kinds  of  circulating  pumps  are  required  for  refrigerating 
apparatus,  apart  from  the  compressor,  which  is  itself  a  pump — 
that  for  the  condensing  water,  and  that  for  the  brine,  where 
brine  is  employed.  The  sizes  of  the  pumps  and  their  arrangement 
hardly  require  any  explanation  to  marine  engineers.  They  will 
depend  upon  the  quantities  of  water  and  brine  to  be  circulated, 
and  the  sizes  and  lengths  of  the  pipes  through  which  they  pass. 
The  pumps  can  be  driven  by  any  convenient  source  of  power. 
With  small  plants  it  is  usual  to  mount  them  on  the  outside  of 
the  tank  which  forms  the  condenser,  and  to  drive  them  from 
the  compressor  crank  shaft.  With  larger  plant,  separate  arrange- 
ments may  be  made.  It  must  be  remembered  that  the  metal  of 
the  brine  pump  becomes  very  cold  and  that  the  moisture  in  the 
atmosphere  condenses  on  it  and  freezes. 

The  work  done  by  the  heat  delivered  to  the  generator  in  the 
absorption  apparatus  is  the  equivalent  of  the  work  done  by  the 
engine  driving  the  compressor,  and  the  economy  of  the  system, 
as  opposed  to  that  of  compression,  turns  upon  this  point — the 
relative  economy  of  using  the  steam  direct,  and  using  it  to 
drive  a  steam  engine  which  in  its  turn  drives  a  compressor. 
The  heat  delivered  to  the  generator  must  be  sufficient  to  con- 
vert the  liquid  ammonia  into  gas,  as  well  as  to  raise  the  tem- 
perature of  the  solution,  so  that  the  gas  may  be  expelled.  A 
proportion  of  this  heat  is  obtained  from  the  heat  delivered  by 


£>4  COLD    STORAGE    ON    BOARD    SHIP. 

the  gas  to  the  water  in  the  absorber,  in  the  act  of  solution, 
and  the  further  this  can  be  carried,  the  more  economical  must 
the  process  be. 

HOW  REFRIGERATING  APPARATUS  IS  MEASURED. 

In  a  previous  part  of  these  articles,  the  terms  one-ton  machine 
and  six-ton  machine  have  been  used.  These  terms  express  the 
manner  in  which  refrigerating  apparatus  is  measured.  A  one- 
ton  machine  is  one  that  will  produce  what  is  called  a  ton  of 
refrigeration  in  twenty-four  hours.  A  ton  of  refrigeration  is 
the  equivalent  of  the  cooling  effect  that  the  melting  of  a  ton  of 
ice  would  produce  in  the  same  time.  Ice  requires,  as  mentioned, 
the  abstraction  of  142  heat  units  for  every  pound  of  water  that 
is  frozen,  from  and  at  32  degrees  F.  In  melting,  each  pound  of 
ice  will  absorb  142  heat  units,  and  a  ton  of  ice  therefore  will 
absorb,  on  American  measurement,  284,000  units,  and  on  British 
measurement,  318,080  units — America  using  the  simpler  short  ton 
of  2,000  pounds,  while  the  United  Kingdom  uses  the  old-fashioned 
2,240  pounds.  The  above  figures  mean,  respectively,  11,833  and 
13*253  units  per  hour.  It  is  important  to  remember  this  latter 
fact. 

It  may  happen  that  it  is  required  to  extract  heat  very  rapidly. 
The  most  rapid  rate  for  a  one-ton  machine  is  given  by  the  above 
figures,  the  capacity  of  larger  or  smaller  machines  being  in  direct 
proportion.  It  is  also  important  to  note  that  a  one-ton  machine 
will  not  make  one  ton  of  ice  in  twenty-four  hours.  It  is  usually 
reckoned  that  the  quantity  of  ice  which  will  be  made  by  a 
machine  of  any  given  size  is  one-half  its  rating.  The  reason  is, 
there  are  losses  between  the  refrigerating  plant  and  the  water 
that  is  being  frozen,  added  to  which  work  has  to  be  done  in 
abstracting  heat  from  the  water  in  reducing  it  to  freezing  point, 
and  from  the  ice  after  it  is  actually  frozen.  The  old  rule  holds 
here  as  everywhere — do  not  cut  your  plant  too  fine ;   and  another 


HOW   REFRIGERATING    APPARATUS    IS    MEASURED. 


65 


rule  which  is  equally  true — you  can  afford  to  work  closer  to  the 
rated  capacity  of  any  plant,  the  greater  care  you  give  it. 


HASLAM    NAVAL    REFRIGERATING   SET.    MOUNTED    IN    TANDEM. 


Practice  allows  a  one-ton  machine  for  a  cold  chamber  ranging 


66  COLD   STORAGE   ON   BOARD   SHIP. 

from  a  capacity  of  800  cubic  feet  up  to  3,000  cubic  feet,  a  two-ton 
machine  from  3,000  to  6,000  cubic  feet,  a  four-ton  machine  from 
10,000  to  20,000  cubic  feet,  and  so  on. 

THE  POWER  REQUIRED  FOR  REFRIGERATING  APPARATUS. 

The  power  required  varies  from  0.3  horsepower  per  ton  of 
refrigeration,  up  to  1.7  horsepower.  Small  plants  require  more 
power  in  proportion  than  large  plants,  and  more  power  is  re- 
quired, usually,  in  hot  climates  than  in  temperate.  Small  plants 
are  allowed  from  one  horsepower  up  to  three  horsepower  for  a 
one-ton  machine,  the  proportion  falling  as  the  size  is  increased. 
The  power  required  increases  as  the  condenser  pressure  increases, 
and  that  is  one  reason  why  more  power  is  required  in  hot  cli 
mates.  In  addition,  more  power  is  required  because  more  water 
has  to  be  circulated,  when  its  initial  temperature  is  higher. 

COOEING  WATER. 

A  point  that  is  of  importance  here  is  to  note  that  if  sea 
water  is  employed  its  specific  heat  is  lower  than  that  of  pure  water. 
It  may  easily  have  a  specific  heat  as  low  as  0.95,  which  means 
that  a  little  over  5  percent  additional  cooling  water  must  be 
allowed.  For  cooling  water  having  an  initial  temperature  of  55 
degrees  F.,  and  having  its  temperature  raised  to  80  degrees  F., 
the  following  quantities  of  pure  water  are  required:  for  the 
ammonia  condenser,  50  gallons  an  hour  per  ton  of  refrigeration, 
and  with  carbonic  acid  about  15  percent  more,  according  to  the 
Linde  Company's  experiments;  larger  quantities  are  required, 
as  explained,  when  the  initial  temperature  is  higher.  Approxi- 
mately, ten  gallons  per  ton  additional  will  be  required  for  every 
five  degrees  increase  in  initial  temperature,  unless  the  final  tem- 
perature can  also  be  increased,  and  again  larger  quantities  for 
carbonic  acid. 


FORMS    OF    APPARATUS    FOR    USE    ON     BOARD    SHIP. 


67 


WEST     CARBONIC    ANHYDRIDE     COMPRESSOR    AND     CONDENSER. 


FORMS   OF   APPARATUS    FOR   USE   ON   BOARD    SHIP. 


The  apparatus  that  is  most  suitable  for  ship  board  use  is  the 
one  that  occupies  the  smallest  space,  provided  other  things  are 
equal.  Some  forms  of  apparatus  are  made  very  compact,  the 
casting  upon  which  the  compressor  and  engine  are  built  inclos- 
ing the  condenser  for  the  refrigerator,  while  the  condenser  for 


68  COLD   STORAGE   ON    BOARD   SHIP, 

the  steam  engine  which  drives  the  compressor  is  carried  over- 
head. The  driving  arrangements  are  also  made  very  compact,  the 
steam  engine  bed  being  extended  at  the  back  of  the  cylinder,  and 
the  tail  rod  of  the  piston  being  used  as  the  piston  rod  of  the 
compressor.  A  useful  form  of  apparatus  that  has  been  fitted 
into  some  ships  has  two  steam  cylinders,  mounted  on  one  bed 
plate,  each  driving  its  own  carbonic  acid  compressor  by  the  tail 
rod  of  its  piston  as  explained  above,  and  each  having  its  own 
steam  and  its  own  carbonic  acid  condenser. 

OTHER   APPLICATIONS   OF   REFRIGERATION    ON   BOARD    SHIP. 

One  useful  application  of  cold  temperature  is  to  keep  low  th* 
temperature  of  the  carbonic  acid  that  is  stored.  The  refrigerants 
employed  are  always  carried  in  strong  iron  or  steel  bottles,  which 
are  tested  to  a  pressure  several  times  that  which  they  are  likely 
to  have  to  stand;  but  it  is  well  to  keep  the  spare  bottles  cool. 
With  increased  temperature  the  gas  endeavors  to  expand,  and  if  it 
is  not  able  to  do  so,  the  pressure  increases  inside  the  bottles. 
With  iron  and  steel  it  is  a  very  difficult  matter  to  be  sure  that 
there  are  no  flaws,  hidden  away  in  the  body  of  the  metal,  which 
the  increased  pressure  would  find.  Also,  stoppers  sometimes  be- 
come faulty  after  a  time.  In  any  case,  it  is  a  very  simple  matter 
to  provide  for  keeping  the  bottles  cool.  A  cupboard  is  built, 
large  enough  to  take  the  spare  bottles  that  are  carried.  It  is 
insulated  in  the  usual  way,  and  has  a  small  grid  of  pipes  carry- 
ing the  refrigerant  or  brine,  as  convenient;  or  it  may  be  cooled 
by  exposure  to  the  current  of  air,  or  a  branch  of  it,  that  is  cooling 
the  cold  chamber. 

COOLING   MAGAZINES   AND  OFFICERS*   AND   MEN'S   QUARTERS. 

Trouble  appears  to  have  arisen  in  the  British  Navy  over  the 
matter  of  cooling  the  magazines.    It  was  reported  some  time  since 


COOLING    MAGAZINES    AND   QUARTERS. 


69 


70  COLD    STORAGE   ON    BOARD    SHIP. 

that  fans  were  put  on  to  cool  the  magazines,  but  they  produced 
trickling  water  on  the  walls,  and  so  had  to  be  abandoned.  With 
refrigerating  apparatus  on  board,  the  problem  should  be  solved 
with  ease.  The  air  entering  the  magazine  should  be  dried  before 
its  entrance,  by  one  of  the  methods  described.  Probably  a  smell 
grid  and  a  small  fan  would  do  the  work  very  well.  But  it  must 
be  remembered  that  for  successful  ventilation  the  air  that  is  dis- 
placed must  be  disposed  of.  It  is  of  no  use  trying  to  force  fresh 
air  into  the  magazine  unless  the  air  already  in  the  magazine  is 
carried  away.  There  must  be  a  complete  ventilating  circuit,  just 
as  there  must  be  a  complete  electrical  circuit,  or  no  action  can 
take  place ;  but  the  atmosphere  may  form  part  of  some  ventilat- 
ing circuits,  just  as  the  ground  forms  part  of  some  electrical 
circuits. 

The  same  remarks  apply  to  cooling  the  officers'  or  men's  quar- 
ters, or  to  cooling  the  'tween  decks,  when  live  cattle  are  carried 
there.  Putting  a  fan  in  somewhere  and  churning  up  the  air  will 
not  ventilate.  It  may  create  drafts,  but  it  will  only  move  the 
air,  not  change  it.  A  current  of  air  brought  down  from  the 
deck,  and  directed  through  the  space  to  be  cooled,  will  cool  to 
the  extent  that  its  temperature  and  the  quantity  available  allow, 
as  explained  in  connection  with  the  cooling  of  air  for  cold  cham- 
bers. But  where  the  atmospheric  air  is  at  a  high  temperature, 
especially  if  it  is  heavily  charged  with  vapor,  it  has  very  little 
cooling  effect.  The  figures  given  above  will  show  this.  If  the 
air  is  cooled  a  few  degrees,  and  dried,  it  will  then  produce  a 
pleasant,  cooling  effect  on  both  man  and  beast,  because,  with  men 
at  any  rate,  nature's  cooling  apparatus,  the  evaporation  of  perspi- 
ration from  the  skin,  can  come  into  play.  This  evaporation  can 
take  pl?ce  in  a  dry  atmosphere,  even  if  it  is  not  a  cool  one. 


FAULTS.  71 

FAULTS. 

The  term  faults,  which  is  a  very  good  one,  is  borrowed  from 
the  practice  of  electrical  engineers,  who  refer  to  a  fault  in  a 
cable,  when  the  insulation  has  been  damaged,  and  possibly  the 
current  refuses  to  pass  the  damaged  spot  in  sufficient  quantity 
to  work  the  apparatus  beyond;  or  to  a  fault  in  the  armature  of 
a  dynamo,  when  the  insulation  has  been  destroyed,  and  the 
armature  refuses  to  furnish  its  proper  pressure,  and  so  on;  and 
the  term  is  used  in  the  same  sense  in  these  articles.  Faults  are 
causes  of  failure,  things  which  happen,  and  which  prevent  appa- 
ratus from  working  properly. 

There  is  nothing  in  cold  storage  apparatus  that  the  marine 
engineer  who  knows  his  work  will  not  be  able  to  master,  if  he 
puts  his  mind  into  it,  and  if  he  will  remember  the  differences  be- 
tween the  freezing  apparatus  and  the  steaming  apparatus.  There 
is  a  great  similarity  between  the  two  in  many  respects,  and  on 
the  other  hand,  there  are  some  very  wide  and  important  differ- 
ences that  must  be  remembered,  if  the  plant  is  to  be  kept  going 
satisfactorily.  A  cold  storage  plant  is  very  much  in  the  nature 
of  a  steam  plant  reversed.  The  cold  store  itself,  or  the  brine 
tank,  or  the  air  cooling  apparatus,  or  whatever  may  receive 
"cold"  from  the  expansion  coils,  stands  very  much  in  the  same 
relation  to  the  whole  plant  as  the  boiler  does  to  the  steam  plant. 

The  refrigerating  agent,  carbonic  acid  or  ammonia,  enters  the 
expansion  coils — the  "refrigerator"  as  it  is  now  more  common 
to  call  it — as  a  liquid,  and  there  becomes  vapor  or  gas.  The 
vapor  or  gas  passes  from  the  expansion  coils  to  an  apparatus, 
very  similar  in  every  respect  to  a  steam  engine,  even  to  the  fact 
that  it  is  often  divided  into  two,  the  process  being  compounded, 
but  there  is  the  important  difference  that  instead  of  the  refrig- 
erant driving  the  piston,  the  piston  drives  it,  compressing  the 
gas  or  vapor,  preparatory  to  its  being  recondensed  into  the  liquid 
form.  Again  the  gas  or  vapor  passes  from  the  cylinder  of  the 
compressor  to  the  condenser,  where  very  much  the  same  thing 


*J2  COLD    STORAGE    ON    BOARD    SHIP. 

happens  as  when  steam  is  condensed  to  water.  The  gas  passes 
through  pipes,  over  which  cooling  water  is  driven,  the  cooling 
water  extracting  the  latent  heat  from  the  gas,  and  reducing  it 
again  to  a  liquid.  But  again  there  is  an  important  difference. 
With  the  cold  storage  condenser  there  is  no  air  pump.  Air 
must  on  no  account  be  allowed  to  enter  the  refrigerating  system. 
As  will  be  explained  later,  its  presence  seriously  lowers  the 
efficiency  of  the  apparatus,  and  one  of  the  most  important  things 
the  "freezer"  engineer  has  to  look  out  for,  is  that  air  shall  not 
get  into  the  system.  The  presence  of  air  also  reduces  the  work 
the  plant  will  do,  the  ''heat  it  will  lift." 

Again,  one  of  the  earliest  things  the  steam  engineer  gets 
knocked  into  him  by  practical  experience,  and  one  of  the  things 
that  the  experienced  engineer  looks  out  for  almost  before  any- 
thing, is  leakage.  It  may  be  fairly  said  that  no  engineer  in 
charge  of  a  steam  plant  can  run  it  economically  who  has  not 
a  "nose  for  a  leak."  The  steam  engineer  learns  to  know  that 
leakage  of  steam  means  waste.  But  with  refrigerating  apparatus, 
leakage  of  the  refrigerating  agent  means  very  much  more  than 
it  does  in  the  case  of  a  leakage  of  steam.  A  leakage  of  steam 
can  be  made  up,  providing  it  is  not  too  great,  by  increased  gen- 
eration of  steam  from  the  boiler.  It  is  merely  a  nuisance,  as  it 
tends  to  increase  the  leakage  path,  and  to  make  a  mess  in  its 
neighborhood,  but  beyond  that  it  merely  means  an  increased 
quantity  of  coal,  and  possibly  water  consumed.  But  with  a  cold 
storage  plant,  leakage  of  the  refrigerant  means,  and  very  quickly, 
a  largely  reduced  efficiency  of  the  system ;  and  other  troubles. 

The  necessary  number  of  heat  units  that  are  to  be  extracted 
from  the  brine,  the  air,  or  the  room,  and  from  the  produce 
itself,  are  absorbed  by  the  conversion  of  a  definite  quantity  of 
the  refrigerant,  carbonic  acid  or  ammonia,  from  the  liquid  to 
the  gaseous  condition,  and  this  is  possible  only  if  a  certain  quan- 
tity of  the  liquid  is  present,  and  is  allowed  to  pass  through  the 
expansion  valve  in  each  unit  of  time,  or  at  each  stroke  of  the 


FAULTS.  73 

compressor.  If  the  system  is  short  of  refrigerant,  as  it  will  be 
if  a  leak  is  allowed  to  be  set  up,  the  requisite  quantity  of  liquid 
is  not  available,  and  the  refrigerant  passes  through  the  expan- 
sion valve,  partly  as  a  liquid  and  partly  as  a  gas.  The  difference 
between  the  cooling  properties  of  the  refrigerant,  as  a  gas  and 
as  a  liquid,  is  enormous.  Every  pound  of  liquid  ammonia  that 
is  converted  into  gas  absorbs  in  the  neighborhood  of  500  heat 
units  in  the  process,  while  every  pound  of  carbonic  acid  absorbs 
in  the  neighborhood  of  120  heat  units,  but  the  pound  of  ammonia 
gas  or  carbonic  acid  gas  passing  through  the  expansion  coils  in 
place  of  the  liquid,  will  absorb  less  than  one-half  of  one  heat 
unit.  Hence  the  importance  of  keeping  the  proper  charge  of  the 
refrigerant  present  in  the  system  is  at  once  apparent. 

In  addition  to  that,  as  marine  engineers  are  aware,  when 
ammonia  or  carbonic  acid  is  able  to  leak  out,  air  is  able  to  pass 
in  when  the  plant  is  standing.  The  quantity  of  air  passing  in  in 
any  given  time  may  be  small,  but  every  engineer  knows  the 
enormous  effect  of  the  continued  passage  of  a  very  small  quan- 
tity of  some  troubling  agent,  and  everyone  who  has  had  to  do 
with  pumps  is  aware  of  the  trouble  caused  by  the  ingress  of 
air.  In  the  refrigerating  system  the  entrance  of  air  operates  in 
two  ways.  The  space  occupied  by  the  air  is  at  the  expense  of  a 
certain  quantity  of  the  refrigerant.  In  addition,  air  cannot  be 
liquefied.  It  becomes  heated  under  compression.  It  is  apt  to 
collect  in  parts  of  the  system,  again  in  a  compressed  and 
heated  state,  and  generally  to  give  trouble. 

One  of  the  first  rules  therefore  to  be  observed  by  the  marine 
engineer  who  takes  charge  of  a  refrigerating  apparatus  is  to 
keep  a  very  careful  eye  upon  all  joints,  stuffing  boxes,  glands, 
etc.  Where  the  pipes  carrying  the  gas  enter  the  condenser,  and 
where  the  liquid  leaves  it,  the  glands  through  which  they  pass 
must  be  maintained  absolutely  gas-tight.  And  perhaps  a  more 
important  matter  is  the  question  of  leakage  of  the  refrigerant 
in  the  neighborhood  of  the  piston  rod.     In  the  case  of  the  steam 


74  COLD    STORAGE    ON    BOARD    SHIP. 

engine  a  little  steam  passing  up  by  the  side  of  the  piston  rod 
does  very  little  harm,  but  in  the  case  of  refrigerating  apparatus, 
the  passage  of  the  refrigerating  agent  along  the  piston  rod,  and 
so  to  the  atmosphere  outside,  has  very  serious  results  indeed,  as 
will  be  explained  later  on. 

One  of  the  difficulties  in  the  way  of  finding  leaks  of  carbonic 
acid  or  ammonia  lies  in  the  fact  that  they  do  not  render  them- 
selves visible,  as  steam  leaks  usually  do,  by  condensing.  Car- 
bonic acid  gas  may  be  leaking  into  the  atmosphere  in  the  neigh- 
borhood of  the  compressor,  or  at  other  parts  of  the  apparatus, 
for  a  very  long  time,  and  nobody  will  know  it,  except  by  its 
effect  upon  the  working  of  the  cold  storage  plant.  Carbonic  acid 
gas  is  a  poison,  in  the  sense  that  when  it  is  present  in  certain 
definite  quantities,  animals  are  unable  to  breathe,  but  in  the 
ordinary  engine  room,  where  there  is  a  certain  amount  of  ven- 
tilation, there  may  be  a  comparatively  large  leak  of  carbonic  acid 
gas,  carried  off  by  the  ventilating  air  current,  without  any  dan- 
ger to  anybody,  and  without  any  effect,  even  in  extreme  cases, 
beyond  a  headache.  Ammonia  gas  is  more  easily  detected  by 
its  pungent  odor,  but  even  ammonia  gas  may  be  escaping  in 
small  quantities,  and  be  carried  off,  unnoticed,  by  the  ventilating 
air  current,  and  be  creating  a  considerable  shortage  in  the  sys- 
tem, without  anybody  suspecting  it. 

For  carbonic  acid  gas  the  rule  is,  to  cover  joints  and  all  places 
where  leakage  may  take  place,  with  soap  and  water.  If  there  is 
a  leak,  soap  bubbles  are  formed.  With  ammonia  the  nose  is 
usually  a  very  good  apparatus  for  testing,  but  if  a  more  certain 
one  is  required,  a  piece  of  sulphur  held  on  the  end  of  a  stick 
and  lighted,  the  burning  sulphur  being  held  in  the  neighborhood 
of  joints  where  leaks  are  suspected,  will  show  their  presence 
immediately  by  creating  dense  white  fumes. 


ft 
WATCH    THE   GAGES.  75 

WATCH   THE   GAGES. 

In  this  matter  the  marine  engineer  will  recognize  the  similarity 
with  his  work,  in  connection  with  steam  plants.  Just  as  he  watches 
the  steam  gage  and  the  water  gage  on  his  boiler,  so  his  success 
in  keeping  his  refrigerating  plant  in  good  order  depends  largely 
.upon  his  watching  the  gages  upon  the  different  parts  of  the 
apparatus.  The  gages  in  connection  with  a  refrigerating  plant 
have  also  a  greater  importance,  even,  than  in  connection  with  a 
steam  plant.  An  intelligent  interpretation  of  the  gages  will  tell 
a  good  deal  of  what  is  going  on  in  the  refrigerating  plant,  and 
will  enable  the  proverbial  stitch  in  time  to  be  put  in.  Steam 
engineers  are  familiar  with  the  fact  that  each  steam  pressure 
corresponds  to  a  certain  temperature  of  the  steam,  and  the  same 
thing  rules  with  the  carbonic  acid  and  ammonia  employed  in 
refrigerating  plants.  Each  pressure  corresponds  to  a  certain 
temperature. 

It  is  usual  to  place  gages  marked  in  pressures  and  the  cor- 
responding temperatures  on  two  eccentric  circles  on  what  are 
termed  the  high-pressure  and  low-pressure  sides  of  the  plant. 
It  will  be  remembered  that  the  carbonic  acid  or  ammonia  comes 
into  the  compressor  in  the  form  of  a  gas,  and  is  compressed  and 
delivered  to  the  condenser  at  a  considerably  higher  pressure. 
The  condenser  is  therefore  the  high-pressure  side,  and  the  gage 
is  usually  fixed  at  the  entrance  to  the  condenser.  The  liquid,  it 
will  be  again  remembered,  passes  through  the  expansion  valve, 
or  regulator,  as  it  is  often  called,  into  the  expansion  coils  or 
refrigerator,  and  is  there  reconverted  into  gas  with  a  corre- 
sponding fall  in  pressure  from  that  at  the  entrance  to  the  con- 
denser. This  side,  therefore,  is  the  low-pressure  side.  The 
low-pressure  side  may  be  taken  to  be  that  portion  of  the 
apparatus  between  the  regulator  and  the  suction  valve  of  the 
compressor;  while  the  high-pressure  side  is  between  the  delivery 
valve  of  the  compressor  and  the  condenser  side  of  the  regulator. 


76  COLD    STORAGE   ON    BOARD    SHIP. 

It  is  usual  to  place  another  gage  on  the  suction  side  of  the  ex- 
pansion coils,  marked  also  in  pressures  and  the  temperatures 
corresponding. 

It  will  be  noted  that  the  reverse  of  steam  apparatus  mentioned 
above  is  maintained  here,  the  entrance  to  the  condenser  with 
steam  is  the  low-pressure  side,  while  it  is  the  high-pressure  side 
with  refrigerating  apparatus.  The  pipe  through  which  the 
newly  created  vapor  issues  in  the  steam  plant  is  the  high-pres- 
sure, whereas  it  is  the  low-pressure  in  the  refrigerating  plant.  In 
all  refrigerating  plants  there  are  certain  standard  pressures  that 
are  maintained  under  ordinary  conditions,  at  the  entrance  to 
the  condenser,  and  at  the  exit  from  the  expansion  coils.  The 
pressure  at  the  exit  from  the  expansion  coils  is  not  reduced  to 
nothing,  as  might  be  at  first  supposed.  In  fact,  a  little  considera- 
tion will  show  that,  other  things  being  the  same,  the  pressure  on 
the  suction  side  of  the  compressor  is  all  the  better  for  being 
higher.  With  high  suction  pressure  there  is  less  work  for  the 
compressor  to  perform  than  where  the  suction,  pressure  is  low, 
and  therefore  less  coal,  steam,  etc.,  is  consumed  in  compressing 
the  carbonic  acid  or  ammonia. 

The  ordinary  standard  pressures  are  for  carbonic  acid  65  to 
75  atmospheres,  or  955  to  1,100  pounds  per  square  inch  at  the 
entrance  to  the  condenser,  corresponding  with  760  to  86°  F.,  and 
25  atmospheres,  or  367.5  pounds  per  square  inch  at  the  exit  from 
the  evaporating  coils,  corresponding  to  10°  F. ;  with  ammonia, 
from  160  to  180  pounds  condenser  pressure,  and  about  15  pounds 
suction  pressure,  are  the  standard.  The  above  pressures  and 
temperatures  are  for  cooling  water  at  6o°  initial  temperature,  or 
thereabouts,  on  entering  the  condenser.  Where  cooling  water 
of  a  lower  temperature  is  available,  say  at  400  or  500  F.,  the 
condenser  pressure  may  be  lower,  and,  on  the  other  hand,  where 
the  only  cooling  water  available  is  at  a  higher  temperature,  the 
condenser  pressure  also  must  be  higher. 


WATCH    THE    GAGES.  "JJ 

It  was  mentioned  above  that  it  is  an  advantage  to  keep  the 
suction  pressure  high,  within  certain  limits.  It  is  also  an  ad- 
vantage to  keep  the  condenser  pressure  as  low  as  possible,  also, 
of  course,  within  certain  limits.  The  reason  will  be  immediately 
apparent.  The  work  done  in  lifting  the  heat  from  the  cold 
chamber  and  delivering  it  to  the  sea  is  performed  partly  in  the 
compressor,  and  partly  by  the  circulating  pump;  therefore  it  is 
obvious  that  the  less  work  both  the  compressor  and  the  circulat- 
ing pump  have  to  do,  the  less  coal  must  be  burned,  and  the 
cheaper  is  the  storage  produced.  With  low  condensing  pressure 
it  is  evident  that  less  work  has  to  be  done  by  the  compressor 
piston  upon  the  gas  coming  over  from  the  evaporator  coils,  than 
with  the  higher  pressure.  Also,  as  already  explained,  the 
higher  the  pressure  at  which  the  gas  comes  over  from  the  evapo- 
rator, the  less  work  the  compressor  has  to  perform  in  compress- 
ing it  to  a  certain  figure.  It  will  be  understood  that  a  certain 
condenser  pressure  is  necessary  in  all  cases,  before  the  gas  can 
be  converted  to  the  liquid  state,  and  the  lower  the  temperature 
of  the  gas,  that  is  to  say,  the  lower  the  pressure  at  which  the 
cooling  water  will  handle  it,  the  less  work  has  to  be  done  upon 
it.  Further,  the  colder  the  circulating  water,  the  smaller  the 
quantity  that  has  to  be  passed  through  the  condenser  to  extract 
a  certain  quantity  of  heat  from  the  hot  refrigerating  gas,  and, 
therefore,  the  less  work  has  to  be  done  by  the  pump.  Condensa- 
tion, it  will  be  remembered,  means  the  extraction  of  a  certain 
definite  quantity  of  heat  from  the  refrigerant. 

The  rule  in  connection  with  the  condenser  pressure  is,  the 
pressure  must  be  that  which  corresponds  to  a  temperature  10 
degrees  above  that  of  the  cooling  water  at  its  exit  from  the  con- 
denser. The  rule  for  the  pressure  at  the  suction  side  of  the 
compressor,  the  exit  from  the  refrigerator,  is,  the  pressure  should 
be  that  corresponding  to  a  temperature  10  degrees  below  that  of 
the  brine  in  the  brine  tank,  where  the  expansion  coils  are  made 
to  cool  brine,  and  are  not  made  to  act  directly  upon  the  air  of 


78  COLD    STORAGE    ON    BOARD    SHIP. 

the  cold  chamber.  When  the  expansion  coils  act  directly,  either 
upon  air  that  is  being  circulated  through  the  cold  chambers,  or 
upon  the  air  of  the  cold  chambers  themselves,  the  rule  is,  the 
pressure  at  the  exit  of  the  expansion  coils  should  be  that  which 
is  equivalent  to  a  temperature  20  degrees  below  that  of  the  air 
the  coils  are  cooling. 

Tf  the  pressures  named,  with  allowance  for  the  variation  in 
the  temperature  of  cooling  water,  are  shown  on  th°  condenser 
and  on  the  evaporator,  it  is  probable  that  everything  is  working 
properly.  At  any  rate,  it  may  be  taken  almost  as  an  axiom,  that 
when  the  proper  condenser  and  evaporative  pressure  are  show- 
ing, the  compressor,  condenser  and  evaporator  are  working 
satisfactorily,  and  if  there  is  any  fault,  it  is  in  the  chamber  itself, 
or  in  the  brine  circuit.  It  is  for  this  reason  that  the  writer  so 
strongly  urges  the  rule,  "watch  the  gages."  The  "freezer"  engi- 
neer will  watch  his  gages,  allowing  for  the  increase  in  the  con- 
denser pressure  as  he  passes  into  a  warmer  climate,  and  again 
allowing  for  the  decrease  of  pressure  as  he  passes  into  a  colder 
climate,  and  will  know  at  a  glance  that  everything  is  all  right 
up  to  a  certain  point,  or  the  reverse,  just  as  he  does  by  looking 
at  the  gages  on  his  steam  boiler,  etc. 

There  are  certain  signs  which  show  whether  things  are  work- 
ing satisfactorily,  in  addition  to  the  gages.  The  gas  in  the  com- 
pressor is  heated  in  the  act  of  compression,  and  therefore  the 
pipe  through  which  it  makes  its  exit  from  the  compressor  to 
the  condenser  is  slightly  warm  with  ammonia,  and  fairly  hot 
with  carbonic  acid.  On  the  other  hand,  the  gas  which  is  return- 
ing from  the  expansion  coils  to  the  compressor  is  expanding 
during  the  whole  of  its  passage,  and  is  extracting  heat  from 
everything  in  its  neighborhood,  and  it  therefore  follows  that  the 
suction  pipe  leading  to  the  compressor,  and  generally  the  whole 
of  the  compressor  in  the  neighborhood  of  the  suction  valve, 
becomes  covered  with  snow.  The  suction  pipe  and  the  suction 
valve,  being  cooled  by  the  expansion  of  the  gas  inside  them,  cool 


IF    THE    DELIVERY    PIPE    BECOMES    HOT.  79 

the  atmosphere  in  their  immediate  neighborhood,  this  resulting 
in  the  deposit  of  some  of  the  moisture  previously  carried  by  the 
atmosphere,  in  the  form  of  water,  upon  the  pipe,  valve,  etc.,  the 
moisture  being  immediately  frozen.  The  compressor  itself 
should  be  cold.  When  the  delivery  pipe  from  the  compressor  is 
in  the  condition  named,  respectively,,  with  carbonic  acid  or 
ammonia,  and  the  suction  pipe  is  covered  with  frost,  things  are 
usually  going  all  right,  so  far  as  the  refrigerating  plant  is  con- 
cerned, apart  from  the  insulation  of  the  chamber.  If  the  delivery 
pipe  from  the  compressor  becomes  warmer  than  it  should  be,  or 
if  it  becomes  cold,  and  again  if  the  frost  disappears  from  the 
suction  pipe  and  the  neighborhood  of  the  suction  valve,  or  if  the 
compressor  becomes  hot,  these  are  signs  that  something  is 
wrong. 

I 

IF   THE   DELIVERY   PIPE   BECOMES    HOT. 

If  the  delivery  pipe  becomes  hot,  it  is  a  sign  that  the  liquid 
refrigerant  is  not  passing  through  the  regulator  valve  as  rapidly 
as  it  ought  to  be,  there  being  an  increased  pressure  in  front  of 
the  gas  that  is  coming  from  the  compressor,  and  therefore  in- 
creased heat.  If  at  the  same  time  the  frost  either  wholly  or 
partially  disappears  from  the  suction  valve  of  the  compressor, 
it  is  usually  a  sign  that  the  regulator  valve  is  not  open  suffi- 
ciently wide.  Sufficient  liquid  is  not  passing  through  the  system 
to  do  the  work  required  of  it,  and  the  remedy  is  to  open  the 
regulator  valve  a  little  wide-.  The  regulator  valve  is  a  very 
delicate  part  of  the  apparatus,  and  it  will  be  understood  that  a 
very  small  turn,  either  to  open  or  close,  has  a  comparatively 
large  effect  upon  the  delivery  of  liquid  to  the  expansion  coils. 

On  the  other  hand,  the  effect  of  either  opening  or  closing  the 
regulator  valve,  more  or  less,  is  not  apparent  for  several  minutes. 
If  the  delivery  pipe  remains  hot  after  the  regulating  valve  has 
been    opened    wide,    it    is    a    sign    that    there    is    not    sufficient 


80  COLD    STORAGE   ON    BOARD    SHIP. 

refrigerant  in  the  system.  The  cooling  effect  on  the  compressor, 
the  suction  valve,  etc.,  and  later  on  the  delivery  valve,  is  due  to  the 
continuous  evaporation  of  the  liquid,  that  is  going  on  right  from 
the  regulator  valve  into  the  compressor.  As  will  be  seen  later, 
it  is  most  important  that  the  compressor  shall  be  maintained 
cool. 

If  there  is  not  the  proper  quantity  of  the  refrigerant  in  the 
system,  as  explained  above,  it  not  only  lowers  the  efficiency  of 
the  system,  but  it  tends  to  upset  the  working  of  the  system 
generally.  A  little  consideration  will  show  this  very  clearly. 
The  condenser  performs  two  offices.  It  is  a  reservoir  of  the 
liquid  refrigerant,  and  a  condenser  of  the  gas  into  the  liquid 
state.  Its  office  as  a  reservoir  is  often  assisted  by  a  receiver, 
into  which  the  liquid  is  passed  after  leaving  the  condenser;  and, 
where  a  ship  is  much  in  the  tropics,  it  is  a  wise  plan  to  employ 
a  receiver,  and  it  is  also  wise  to  arrange  to  cool  the  liquid 
refrigerant  after  it  leaves  the  condenser,  which  may  be  done  by 
passing  the  circulating  water  over  the  pipe  leading  from  the 
condenser  to  the  receiver.  The  receiver  and  the  condenser  to- 
gether, however,  hold  the  refrigerant  in  three  conditions,  the 
liquid,  the  gaseous,  and  the  transition  states,  the  latter  being 
when  it  is  being  formed  into  the  liquid  from  the  gaseous  state. 
The  gas,  it  will  be  remembered,  coming  from  the  compressor,  is 
hot.  It  passes  in  at  the  top  of  the  condenser,  where  it  meets 
the  cooling  water  which  has  passed  over  the  whole  of  the  re- 
mainder of  the  coils  of  pipe  forming  the  condenser,  and  from 
which  it  receives  its  first  cooling. 

The  operation  of  condensing  may  be  taken  to  consist  of  two 
parts — removing  the  heat  of  compression,  and  removing  the 
latent  heat  of  the  gas.  When  the  plant  is  working,  at  each 
stroke  of  the  compressor  a  definite  quantity  of  gas  is  sucked 
from  the  refrigerator  coils,  this  being  made  up  in  the  coils  by  a 
certain  quantity  of  liquid,  sufficient  to  expand  into  the  quantity 
of  gas  removed  by  the  compressor.    If  the  compressor  is  double 


IF    THE    DELIVERY    PIPE    BECOMES    HOT.  8l 

acting,  at  each  stroke  a  certain  quantity  of  gas  is  delivered  to 
the  condenser,  and  it  may  be  taken  that,  when  the  apparatus  is 
working  normally,  during  the  period  of  each  stroke  a  certain 
quantity  of  gas  is  liquefied  and  added  to  the  reservoir  of  liquid, 
equal  to  that  which  has  been  abstracted  by  way  of  the  regulator 
valve,  to  make  up  for  that  which  was  taken  from  the  refriger- 
ator by  the  suction  of  the  compressor. 

If  the  condenser  and  receiver  together  are  short  of  liquid,  the 
working  of  the  system  is  upset,  because  the  liquid  is  abstracted 
by  the  suction  of  the  compressor  faster  than  it  is  replaced  by 
the  action  of  the  condenser.  The  effect  is  not  apparent  imme- 
diately. In  all  these  matters  in  connection  with  refrigerating 
plants,  time  is  an  important  factor,  but  after  a  certain  time  the 
liquid  in  the  condenser  ceases  to  act  as  a  barrier  or  absorber  to 
the  gas  coming  over  from  the  compressor,  and  at  each  suction 
stroke  of  the  compressor,  a  portion  of  the  gas  passes  through 
the  regulator  valve,  with  a  certain  quantity  of  liquid.  As  was 
explained  before,  this  leads  to  an  immediate  fall  in  the  efficiency 
of  the  apparatus,  and  in  the  work  done  by  the  plant  in  cooling 
the  cold  store,  or  whatever  the  arrangement  may  be,  because, 
while  the  liquid  passing  into  the  gaseous  condition  extracts  a 
definite  number  of  heat  units  for  every  pound  of  liquid  evapo- 
rated, the  gas  which  comes  over  has  practically  no  refrigerating 
effect  at  all,  and  it  lowers  the  refrigerating  effect  of  the  liquid 
which  it  accompanies. 

The  fact  that  the  system  is  short  of  liquid,  and  that  the  gas 
is  coming  over  with  the  liquid  to  the  expansion  coils,  may  be 
known  for  certain  by  placing  the  ear  in  the  neighborhood  of 
the  regulator  valve.  When  liquid  only  passes  the  regulator 
valve,  it  makes  a  hissing  sound,  to  which  the  engineer  soon 
becomes  accustomed,  and  which  he  readily  recognizes.  When 
gas  comes  with  the  liquid,  the  hissing  sound  is  accompanied  by 
a  rattling  which  is  also  unmistakable.  When  the  system  is 
short   of   refrigerant   it   will    easily   be    understood   that,   as   a 


82  COLD    STORAGE   ON    BOARD    SHIP. 

portion  of  the  space  in  the  evaporating  coils  is  occupied  by  the  gas 
which  comes  over  from  the  condenser  in  place  of  liquid,  so  also 
the  cooling  effect  upon  the  suction  pipe  and  upon  the  compressor 
itself,  which  depends  upon  the  evaporation  of  the  liquid,  is  also 
lessened,  with  the  result  that  the  frost  is  lost  from  the  suction 
side  of  the  compressor.  In  addition  the  compressor  itself  often 
becomes  very  hot,  this  leading  to  other  troubles,  such  as  the 
destruction  of  the  packing,  leading  again  to  leakage  of  the  re- 
frigerant, to  the  vaporizing  of  the  lubricant,  and  its  being  carried 
over  with  the  gas,  as  vapor  into  the  condenser,  this  giving 
troubles  that  will  be  explained  later  on. 

The  remedy  is  to  add  liquid  to  the  system  in  the  same  manner 
as  when  charging,  adding  carefully  until  the  signs  disappear. 
When  a  shortage  arises,  however,  it  will  always  be  wise  to  find 
out  the  cause.  Leakage,  as  before  explained,  is  one  of  the  pos- 
sible causes.  Another  cause  is  the  possibility  that  oil  has  got 
into  the  system,  as  explained  above ;  a  third  that  air  has  got  in ; 
a  fourth  that  the  cooling  water  is  not  sufficient,  that  the  con- 
denser is  not  doing  its  work  properly;  and  a  fifth,  which  is 
easily  looked  out  for  and  provided  for  when  the  ship  passes  into 
warmer  climates,  that  the  hotter  cooling  water  is  not  doing  its 
work  as  well  as  the  colder  water  of  a  temperate  climate.  A 
little  consideration  will  show  when  the  cooling  water  from  any 
cause  is  insufficient.  If  on  passing  into  the  tropics  the  water 
available  is  hotter,  while  the  circulating  pumps  will  not  allow  of 
a  larger  quantity  being  passed  through  the  condenser  in  the 
proper  proportion,  less  liquid  refrigerant  will  be  formed  during 
the  period  of  each  stroke,  anpl  the  reservoir  of  liquid  will  be- 
come less,  with  the  result  that  after  a  certain  time  the  results 
of  shortage  mentioned  above  will  be  apparent.  The  remedy  is 
to  add  liquid  refrigerant,  as  described  above. 

Anything  which  interferes  with  the  process  of  the  condensa- 
tion of  the  gas  will  also  interfere  with  the  working  of  the  sys- 
tem, and  will  produce  the  same  results  as   a  shortage  of  the 


IF    THE    DELIVERY    PirE    BECOMES    HOT.  83 

reirigerant.  They  will  lead,  in  fact,  to  a  shortage  in  the  system, 
because,  just  as  explained  with  higher  temperature  cooling 
water,  and  with  a  limited  quantity  of  cooling  water,  a  smaller 
quantity  of  the  gas  will  be  converted  into  liquid  in  a  given  time, 
say  within  the  duration  of  a  stroke  of  the  compressor.  Among 
possible  causes  of  interference  with  the  process  of  condensation 
are, — higher  temperature  of  cooling  water,  as  already  explained; 
shortage  of  quantity  of  cooling  water;  inefficient  working  of 
the  cooling  water  circulating  pump;  and  any  deposit  which 
forms  on  the  outside  of  the  condenser  pipes.  Sea  water,  and 
most  cooling  waters,  contain  salts  in  solution,  some  of  which  are 
deposited  upon  the  metal  surfaces  over  which  they  run,  such  as 
the  condenser  pipes,  especially  when  the  pipes  are  hot,  as  they 
must  necessarily  be  in  a  condenser;  and  the  deposit  is  increased 
whenever  the  velocity  of  the  cooling  water  is  decreased. 

The  best  conditions  under  all  circumstances  for  taking  the 
heat  out  of  gas  or  out  of  steam  by  the  aid  of  circulating  water, 
in  a  surface  condenser,  are,  that  the  water  shall  pass  very 
rapidly  over  the  surfaces  of  the  pipes,  on  the  other  side  of  which 
the  gas  or  steam  is  passing,  and  that  the  thickness  of  the  pipes 
shall  be  as  small  as  is  consistent  with  mechanical  strength,  and 
with  the  necessary  ability  to  withstand  the  strains  brought  by 
expansion  and  contraction,  under  changes  of  temperature.  A 
deposit  is  formed  from  the  cooling  water,  as  marine  engineers 
know  to  their  cost.  They  have  it  in  another  form  in  boilers  in 
which  sea  water  is  employed  for  raising  steam.  It  has  a  high 
thermal  resistance,  as  refrigeration  engineers  express  it. 

The  deposit  of  salts  or  scale  opposes  the  passage  through 
itself  of  the  heat,  and  therefore  lessens  the  quantity  of  heat 
taken  by  the  cooling  water  in  a  given  time  from  the  gas  or 
steam  that  is  to  be  cooled.  The  result  is  that,  with  a  given 
quantity  of  cooling  water  passing,  say  with  a  given  capacity  of 
circulating  pump,  a  smaller  quantity  only  of  liquid  refrigerant 
is  produced,  and  the  other  signs  of  shortage  in  the  system  are  in 


84  COLD    STORAGE   ON    BOARD   SHIP. 

evidence.  On  the  other  hand,  anything  which  tends  to  increase 
the  effective  working  of  the  condenser,  such  as  the  presence  of 
a  lower  temperature  of  cooling  water,  instantly  tends  to  lower  the 
condenser  pressure,  because  a  larger  quantity  of  liquid  refriger- 
ant is  produced,  a  larger  quantity  will  be  passing  through  the 
regulator  valve,  unless  it  is  closed  a  little  more  than  previously, 
and  there  will  be  signs  similar  to  those  where  there  is  too  much 
refrigerant  present  in  the  system.  It  need  hardly  be  mentioned 
that  the  lower  the  pressure  in  the  condenser,  the  less  the  work 
the  compressor  has  to  perform,  and  the  less  the  work  the  cool- 
ing water  has  to  perform. 

Hence,  the  "freezer"  engineer  will  watch  the  temperatures  of 
the  delivery  pipe,  the  suction  pipe,  and  the  compressor  itself.  If 
he  finds  his  condenser  pressure  going  up,  and  especially  if  it  is 
accompanied,  as  it  usually  will  be,  by  increased  heat  of  the  de- 
livery pipe,  it  may  be  that  the  refrigerant  is  not  passing  through 
the  regulator  to  the  evaporator  as  quickly  as  it  should;  and, 
again,  this  may  be  caused  by  a  greater  demand  upon  the  cooling 
water  in  the  evaporator  coils,  owing  to  other  causes  in  the  cold 
chamber  which  will  be  dealt  with  further  on. 


TOO    MUCH    REFRIGERANT   IN    THE   SYSTEM. 

It  is  not  often  that  this  arises,  though  cases  have  been  reported. 
There  is  a  certain  definite  quantity  of  refrigerant  that  is  suitable 
for  each  size  of  plant,  each  size  of  compressor,  condenser,  and 
so  on.  The  manufacturers  in  all  cases  give  full  particulars  of 
the  quantity  that  should  be  placed  in  the  system.  All  manufac- 
turers recommend  that  a  slight  excess  should  be  carried,  rather 
than  the  reverse.  With  carbonic  acid  it  appears  not  to  be  easy 
to  carry  a  dangerous  excess,  but  with  ammonia  the  trouble  does 
arise,  though  not  frequently.  In  either  case,  an  excess  of  the 
refrigerant,  up  to  25  percent  of  the  quantity  stated  by  the 
manufacturer,  will  do  no  harm,  and  will  probably  help  to  keep 


IF  THE   DELIVERY   PIPE   BECOMES   COLD.  85 

the  plant  running  efficiently  and  continuously  over  a  longer  time, 
in  the  presence  of  leaks,  than  when  only  the  exact  quantity  has 
been  placed  in  the  system. 

Where,  however,  a  large  excess  of  refrigerant  is  carried,  it 
means  that  a  large  portion  of  the  space  available  in  the  con- 
denser is  occupied  by  liquid,  a  larger  space  than  is  necessary, 
with  the  result  that  the  gas  that  is  coming  over  is  confined  in  a 
smaller  space  than  is  intended.  A  very  excessive  charge  is 
shown  by  considerable  fluctuation  on  the  pointers  of  the  gages. 
With  regular  working,  the  pointers  of  the  gages  go  up  at  each 
stroke,  and  then  return.  With  very  excessive  charge  they 
fluctuate  very  irregularly.  It  may  be  taken  that  anything  which 
throttles  the  delivery  of  the  liquid,  carbonic  acid  or  ammonia, 
in  its  passage  to  the  expansion  coils,  will  increase  the  condenser 
pressure,  and  will  raise  the  temperature  at  the  delivery  pipe. 


IF  THE   DELIVERY   PIPE   BECOMES    COLD. 

If  the  delivery  pipe  from  the  compressor  becomes  cooler  than 
it  should  be,  it  is  a  sign  that  the  liquid  refrigerant  is  passing 
through  the  regulator  valve  in  larger  quantities  than  it  should  do, 
and  the  pressure  at  the  condenser  will  be  lowered,  the  heat  at 
the  delivery  pipe  being  lowered  with  it.  The  remedy  is  to  slightly 
close  the  regulator  valve,  bearing  in  mind  the  remark  made 
above  as  to  closing  or  opening  to  a  very  small  extent  under  these 
circumstances,  and  as  to  the  effect  not  being  apparent  for  a  few 
minutes. 


WHAT  FOLLOWS   FROM   A   HOT  COMPRESSOR. 

It  has  been  explained  that  the  normal  condition  of  the  com- 
pressor when  the  apparatus  is  working  properly,  requires  the 
body  of  the  compressor  to  be  cold,  the  suction  valve  and  pipe, 
and  sometimes  parts  of  the  compressor  in  the  neighborhood  of 


86  COLD    STORAGE   ON    BOARD    SHIP. 

the  suction  valve,  being  covered  with  frost.  If  the  system  be- 
comes short  of  liquid,  and  if  it  is  not  working  properly,  that  is 
to  say,  if  a  sufficient  quantity  of  the  liquid  refrigerant  does  not 
pass  into  the  evaporator  coils,  and  the  evaporation  does  not 
continue  in  a  minor  degree  right  down  to  the  suction  valve,  the 
frost  on  the  suction  pipe  is  lost,  and  the  compressor  itself  gradu- 
ally gets  hot. 

As  marine  engineers  will  understand,  the  natural  result  of 
working  a  piston  in  a  cylinder  is  the  generation  of  heat,  unless 
means  are  taken  to  prevent  it.  Further,  those  who  have  had  to 
do  with  air  compressing  machinery  know  also  that  the  natural 
result  of  compressing  any  gas  is  the  liberation  of  heat  in  the  gas 
itself,  due  to  the  compression;  the  heat  so  liberated  being  com- 
municated to  the  compressor.  With  refrigerating  apparatus,  any 
heat  in  the  compressor,  as  will  be  explained,  is  fatal  to  the 
effective  working  of  the  apparatus,  and  it  is  for  this  reason  that 
a  sufficient  quantity  of  the  liquid  refrigerant  is  always  allowed 
to  pass  through  the  evaporator  coils  to  bring  a  certain  cooling 
effect  right  back  to  the  compressor  itself,  and  to  keep  the  com- 
pressor cool. 

The  compressor,  though  very  like  a  steam  cylinder,  and  still 
more  like  an  air  compressor  cylinder,  differs  from  both  in  one 
very  important  particular  already  dealt  with,  viz.,  that  on  no 
account  must  the  gas  be  allowed  to  leak,  since  leakage  leads  to 
shortage,  and  the  consequences  of  that  have  been  explained.  To 
meet  this  requirement,  the  piston  rod  of  the  compressor  works 
in  a  long  gland,  designed  expressly  to  prevent  the  egress  of  even 
the  smallest  quantity  of  the  gas.  It  consists  practically  of  four 
parts.  There  are  two  sets  of  packing,  carefully  cut  and  arranged 
in  the  gland,  so  that  the  piston  rod  will  work  easily  in  them, 
and  at  the  same  time  they  will  prevent  the  egress  of  gas.  Be- 
tween the  two  sets  of  packing  there  is  nearly  always  a  lantern 
arranged  to  be  rilled  with  a  special  lubricating  oil,  the  oil  itself 
being  maintained  in  the  lantern  under  pressure.     The  packing  is 


WHAT  FOLLOWS   FROM    A    HOT  COMPRESSOR.  87 

soaked  in  the  special  lubricating  oil,  and  in  some  forms  of 
apparatus  there  is  an  oil  chamber  outside  of  the  outside  packing. 
It  is  absolutely  necessary  that  the  piston  rod  shall  run  perfectly 
freely,  but  gastight  in  the  gland,  and  that  it  shall  always  be 
absolutely  bright. 

If  from  any  cause  the  piston  rod  becomes  hot,  the  immediate 
consequence  is,  the  packing  becomes  damaged,  and  gas  com- 
mences to  escape,  this  leading  to  a  further  damage  of  the  packing, 
and  so  on.  The  same  result  will  follow  if  the  packing  is  allowed 
to  become  deteriorated,  if  it  is  not  changed  periodically  when  it 
shows  signs  of  deterioration,  and  also  if  it  is  not  screwed  up 
tight  in  the  gland.  On  the  other  hand,  great  care  is  necessary 
in  fitting  the  packing  into  its  place,  and  in  screwing  the  gland  up 
when  the  packing  is  in.  It  will  easily  be  understood  by  marine 
engineers  that  where  a  very  small  fraction  of  an  inch  out  of  line 
will  produce  sufficient  friction  to  heat  the  piston  rod,  and  all 
that  follows,  great  care  and  some  skill  are  necessary  in  dealing 
with  this  matter. 

In  addition  to  this,  the  piston  itself  is  packed  with  leathers,  and 
there  is  also  a  special  lubricating  oil  always  employed  to  lubri- 
cate the  piston.  For  carbonic  acid,  glycerine  of  a  certain  con- 
sistency and  of  a  certain  purity  is  recommended  by  some  makers, 
while  others  prefer  a  special  oil  sold  by  the  Vacuum  Oil  Com- 
pany. For  ammonia  compressors,  special  oils  are  again  em- 
ployed, recommended  by  the  different  manufacturers.  Sulphu- 
rous acid  compressors,  which,  so  far  as  the  writer  is  aware,  have 
not  been  employed  on  board  ship,  have  the  great  advantage  that 
the  liquid  itself  is  a  lubricant. 

Outside  of  the  compressor  and  connected  to  the  delivery  pipe 
is  an  oil  separator,  whose  office  is  similar  to  that  of  steam  oil 
separators,  but  of  very  much  greater  importance.  Its  office  is  to 
extract  any  oil  which  is  carried  over  with  the  gas  from  the 
compressor.  If  any  oil  is  carried  into  the  system,  as  mentioned 
above,  it  leads  to  the  same  results  that  have  been  described  in 


OO  COLD    STORAGE   ON    BOARD    SHIP. 

connection  with  shortage  of  the  refrigerant.  It  leads  to  a  short- 
age, by  taking  the  place  of  a  portion  of  the  refrigerant,  and 
sometimes  by  combining  with  a  portion  of  the  refrigerant.  If 
the  compressor  is  allowed  to  become  hot,  as  was  explained  above, 
the  lubricating  oil  may  become  vaporized,  and  a  small  portion 
will  be  carried  over  with  the  gas  into  the  condenser,  it  not  being 
trapped  by  the  separator  in  the  way  that  the  ordinary  lubricating 
oil  is.  In  the  ordinary  way,  when  the  compressor  is  working 
cold,  the  lubricating  oil  that  is  carried  over  is  in  a  finely  divided 
state  in  small  globules,  just  as  water  is  carried  over  from  the 
boiler  during  the  generation  of  steam;  and  it  is,  or  should  be, 
got  rid  of  by  the  oil  separator,  providing  this  is  properly  looked 
after. 

With  ammonia  compressors,  also,  there  is  another  and  more 
serious  danger,  when  the  compressor  becomes  hot.  At  a  certain 
temperature  ammonia  gas  is  resolved  into  its  constituents.  Am- 
monia gas,  it  will  be  remembered,  is  a  compound  whose  mole- 
cules are  formed  of  one  atom  of  nitrogen  gas,  and  three  atoms 
of  hydrogen  gas.  At  a  temperature  of  900  degrees  F.  the 
ammonia  gas  becomes  nitrogen  and  hydrogen,  and  these,  being 
incompressible  at  the  temperatures  and  pressures  ruling  in  the 
ammonia  compression  system,  remain  as  permanent  gases  in  the 
system,  giving  rise  to  the  same  troubles  as  does  air.  They  get 
into  pockets  in  the  system,  being  compressed  there ;  they  take  up 
space  that  should  be  occupied  by  the  ammonia  gas;  and  under 
certain  conditions  they  may  lead  to  explosion. 

GETTING  OIL  AND   FOREIGN    BODIES   OUT  OE  THE   SYSTEM. 

There  is  a  draw-off  cock  attached  to  the  oil  separator  in  all 
cases,  and  it  should  be  drawn  off  periodically.  The  frequency 
of  the  drawing  off  will  vary  with  different  conditions,  but  the 
engineer  can  hardly  go  wrong  in  drawing  it  off  more  or  less 
continuously.     If  it  is  not  drawn  off  the  receptacle  into  which  it 


GETTING   OIL   AND   FOREIGN   BODIES  OUT  OF   THE   SYSTEM.  &} 

falls  becomes  filled  up,  and  the  natural  consequence  is  an  increas- 
ing quantity  of  oil  carried  over  into  the  condenser.  If,  either 
from  this  cause,  from  the  compressor's  becoming  hot,  or  from 
any  other  cause,  oil  is  found  in  the  system,  the  first  thing  to  be 
done  is  to  endeavor  to  draw  it  off  at  the  separator  by  continuous 
attention.  If  this  fails,  it  must  be  drawn  out  of  the  system  by 
breaking  a  joint,  first  between  the  condenser  and  the  regulator 
to  drive  the  oil  out  of  the  condenser  coils,  and  afterwards  be- 
tween the  evaporator  and  the  compressor  to  drive  the  oil  out  of 
the  evaporator  coils. 

While  the  oil  is  being  driven  out  of  the  condenser  coils,  the 
whole  of  the  charge  must  be  carried  over  to  the  evaporator  coils, 
particularly  with  ammonia,  and  this  is  accomplished  by  opening 
the  regulator  valve  wide,  and  closing  the  suction  cock.  And 
when  the  oil  is  being  driven  out  of  the  evaporator  coils,  the 
charge  must  be  carried  over  into  the  condenser  coils,  by  closing 
the  regulator  valve  and  running  the  compressor  slowly  until  the 
gage  on  the  evaporator  shows  a  vacuum. 

If  the  condenser  or  evaporator  coils  appear  to  be  in  a  very  bad 
state  inside,  as  shown  by  very  irregular  working,  it  will  be  nec- 
essary to  blow  them  both  through  with  steam  first,  and  then  with 
air.  When  a  machine  is  first  put  into  service,  after  it  has  been 
set  up,  it  should  always  be  subjected  to  a  compressed  air  test,  to 
see  that  all  is  in  order,  all  joints  tight,  and  so  on;  and  the  same 
rule  applies  whenever  the  system  is  opened  for  cleaning.  It  will  be 
understood  that  the  same  trouble  mentioned  in  connection  with 
the  deposit  on  the  outside  of  the  condenser  coils  may  also  arise 
from  deposit  on  the  inside  of  both  condenser  and  evaporator 
coils,  from  the  oil  that  has  been  carried  over.  Also,  it  is  a  rule 
that,  before  the  machine  is  started,  either  when  first  put  into 
service,  or  when  taken  apart  for  cleaning,  the  cylinder,  the 
valves,  and  all  pipes  that  can  be  got  at,  are  thoroughly  cleaned 
out,  and  all  grit  and  foreign  substances  removed. 

When    the    condition    of    the    inside    of    either    condenser   or 


90  C0U>    STORAGE    ON    BOARD    SHIP. 

evaporator  coils  becomes  bad,  as  explained,  the  system  is  opened 
up  by  breaking  the  joints  of  the  condenser  to  .the  delivery  pipe, 
and  to  the  regulator,  and  the  connection  of  the  evaporator  coils 
to  the  regulator  and  to  the  suction  pipe.  Steam  from  any  con- 
venient source  is  employed  in  any  convenient  way,  to  blow 
through  each  of  the  coils  in  succession,  until  all  the  foreign 
matter,  oil  and  so  on,  has  been  thoroughly  blown  out.  After 
this  has  been  done,  and  when  the  engineer  has  thoroughly  satis- 
fied himself  that  no  foreign  substance  remains,  the  system  is 
connected  up  again,  all  joints  being  made  except  one  at  the  suc- 
tion pipe.  The  compressor  is  then  run  slowly,  air  being  drawn 
into  the  system,  and  compressed  to  200  pounds  per  square  inch. 
The  broken  joint  is  then  remade,  and  the  system  is  allowed  to 
remain  subject  to  this  compressed  air  pressure  for  some  hours, 
all  joints  being  carefully  examined  during  the  process,  and  the 
gages  watched. 

It  should  be  noted  here  that  the  gages  will  slightly  fall  after 
the  compressor  is  stopped,  owing  to  the  fact  that  the  air  has 
become  heated  while  the  compressor  is  at  work,  the  pressure 
thereby  rising;  while  after  the  compressor  is  stopped,  the  whole 
apparatus  radiates  heat.  The  air  thence  becoming  cooler,  con- 
tracts, and  the  gage  pressures  fall.  All  joints,  and  all  points 
where  leakage  will  be  suspected,  should  be  painted  with  a  lather 
of  soap  and  water,  as  explained  before,  and  bubbles  looked  out 
for. 

To  drive  the  air  out  of  the  system,  when  all  joints  are  good, 
the  methods  employed  with  ammonia,  and  with  carbonic  acid,  are 
slightly  different.  It  does  not  matter  if  a  small  quantity  of  car- 
bonic acid  gas  is  delivered  into  the  atmosphere  of  the  engine 
room.  The  small  quantity  that  will  be  present  does  no  harm, 
and  it  forms  a  ready  and  certain  method  of  insuring  that  the 
air  is  all  got  out.  With  ammonia,  however,  it  is  not  permissible 
to  allow  any  of  the  gas  to  escape  into  the  atmosphere.  Hence 
the  methods  are  as  follows: 


GETTING  OIL  AND  FOREIGN  BODIES  OUT  OF  THE  SYSTEM.  91 

With  carbonic  acid,  the  joint  between  the  condenser  and  the 
regulator  is  broken,  and  the  air  is  pumped  out  of  the  system 
through  this  joint.  The  system  is  then  partly  charged  with  car- 
bonic acid,  and  a  certain  quantity  of  the  gas  is  blown  through 
the  condenser  coils  into  the  atmosphere,  to  waste;  the  result 
being  that  the  system  is  completely  freed  from  air. 

With  ammonia  the  method  adopted  is  as  follows:  The  main 
delivery  stop  cock  is  closed,  and  the  small  cock  on  the  delivery 
side,  the  one  that  is  usually  connected  to  the  gage,  opened,  the 
gage  pipe  having  been  disconnected  if  necessary,  and  all  other 
valves  and  cocks  opened,  except  those  leading  to  the  atmosphere. 
The  compressor  is  then  run  very  slowly,  and  the  air  is  gradually 
withdrawn  from  all  parts  of  the  system,  and  forced  out  through 
the  small  stop  cock  mentioned,  the  gages  recording  the  fact  by 
the  gradually  decreasing  pressures.  The  fact  that  the  air  is  all 
exhausted  is  known  by  the  gages  indicating  a  vacuum,  and  by 
the  gradually  decreasing  noise  which  the  air  issuing  from  the 
small  stop  cock  makes. 

As  soon  as  the  air  has  all  been  driven  out,  the  small  stop  cock 
should  be  closed,  and  the  system  at  once  charged  with  ammonia 
in  the  manner  described  in  the  manufacturers'  directions.  On  no 
account  should  a  vacuum  be  maintained  after  the  air  has  all  been 
expelled  from  the  system.  Many  engineers,  when  they  have  had 
trouble  with  their  plants,  with  oil  and  foreign  bodies,  have  made 
the  great  mistake,  after  they  have  blown  through  with  steam  and 
with  air,  of  pumping  a  vacuum,  and  allowing  the  vacuum  to  re- 
main for  a  number  of  hours.  This  is  wrong,  as  wrong  as  it  can 
be,  as  it  almost  invariably  leads  to  the  entrance  of  air  into  the 
system,  and  to  the  troubles  attendant  thereon.  Keep  the  air 
pressure  on  as  long  as  convenient,  until  you  have  made  all  the 
joints  quite  good,  but  as  soon  as  you  have  got  all  the  air  out,  get 
rid  of  the  vacuum  by  putting  a  charge  in. 

Another  point  that  should  perhaps  be  mentioned,  when  the 
compressor  is   run   for  the  compressed  air  test,   is  that,  if  the 


Q2  COLD    STORAGE   ON    BOARD    SHIP. 

delivery  pipe  and  the  compressor  itself  become  hot,  the  com- 
pressor should  be  immediately  stopped,  the  plant  allowed  to  cool 
down,  overhauled,  and  the  whole  process  gone  over  again. 

Charging  with  ammonia  or  carbonic  acid  is  a  very  simple 
affair.  The  gas  is  contained  in  strong  steel  bottles  with  a  regu- 
lating valve,  to  which  a  flexible  or  bent  metal  tube  is  applied 
when  the  gas  is  to  be  taken  from  it,  the  other  end  of  the  tube 
being  connected  to  the  charging  valve  on  the  system,  which  is 
situated  sometimes  close  to  the  regulating  valve,  and  sometimes 
on  the  other  side  of  the  evaporator  coils.  Only  the  purest  and 
most  perfectly  anhydrous  carbonic  acid  or  ammonia  must  be  em- 
ployed. This  is  one  of  the  most  important  points  in  connection 
with  cold  storage  work.  It  does  not  pay  to  employ  cheap  re- 
frigerant, if  cheapness  means  impurity.  In  the  working  of  the 
system  the  impurities  get  separated  out.  They  sometimes  appear 
as  permanent  gases,  sometimes  form  a  deposit  on  the  inside  of 
the  condenser  or  refrigerator  pipes,  and  generally  cause  trouble. 

It  is  always  wise  to  put  the  flask  of  refrigerant  upon  a  scale, 
when  charging  the  system.  This  enables  the  engineer  to  see 
exactly  how  much  he  has  passed.  When  the  connection  is  made 
between  the  flask  and  the  system,  the  cock  on  the  flask  may  be 
opened  gradually,  the  regulator  valve  of  the  system  being  closed, 
and  the  gas  gradually  allowed  to  pass  in,  this  being  shown  by 
two  things,  the  weight  of  the  flask  gradually  decreasing  and 
hoar  frost  commencing  to  form  on  the  outside  of  the  flask.  When 
about  a  quarter  of  the  refrigerant  contained  in  the  flask  has  been 
carried  over  into  the  system,  the  process  may  be  assisted  by 
slightly  warming  the  flask,  but  great  care  should  be  exercised  in 
performing  this  operation,  and  it  should  never  be  done  until  the 
bottle  is  partially  emptied. 

It  is  wiser,  in  charging  the  system,  to  err  on  the  side  of  a 
small  charge  at  first,  as  it  is  easy  to  increase  the  charge  if 
required.  After  charging,  the  compressor  is  run  at  full  speed 
with  the  cooling  water  running  over  the  condenser  for  a  certain 


TO   TEST    AMMONIA    FOR   PURITY.  93 

time,  and  then  the  compressor  is  stopped,  and  the  system  allowed 
to  remain  at  rest,  except  that  the  cooling  water  continues  to  pass 
over  the  condenser.  The  object  of  this  is  to  allow  any  air  re- 
maining in  the  system  to  rise  to  the  top  of  the  condenser.  This 
air,  in  the  case  of  ammonia  machines,  is  carried  off  from  a  purge 
cock  place  for  the  purpose  at  the  top  of  the  condenser  coils,  to 
which  a  flexible  rubber  tube  should  be  attached,  the  other  end 
of  the  tube  being  led  into  a  vessel  of  water,  the  end  of  the  tube 
being  under  water.  When  the  purge  cock  is  open,  the  air  will 
come  away,  and  will  be  seen  in  bubbles  in  the  water  in  the  vessel, 
and  there  will  be  no  smell  as  long  as  air  is  coming.  When  all 
the  air  has  been  driven  out,  and  ammonia  commences  to  pass,  its 
own  particular  smell  will  be  noticed,  and  the  purge  cock  should 
be  immediately  closed. 

TO    TEST   AMMONIA   FOR   PURITY. 

Draw  off  into  a  stoppered  flask  with  a  bent  tube,  a  small  quan- 
tity of  the  ammonia  to  be  tested,  being  careful  that  none  of  the 
snow  formed  on  the  tube  goes  over  into  the  flask.  The  snow  is 
formed  on  the  tube,  in  all  these  cases,  by  the  sudden  lowering  of  the 
temperature  on  the  outside  of  the  tube,  due  to  the  evaporation 
of  the  ammonia  inside  the  tube;  the  lowering  of  the  temperature 
of  the  air  in  the  neighborhood  of  the  tube  leading  to  the  deposit 
of  moisture,  and  its  immediate  freezing.  After  drawing  off  the 
small  quantity  of  ammonia  into  the  flask,  allow  it  to  evaporate. 
If  it  is  pure,  the  whole  of  the  substance  in  the  flask  will  dis- 
appear. If  anything  remains  in  the  flask,  it  consists  of  impuri- 
ties, such  as  water  or  organic  substances.  Organic  impurities 
are  detected  by  their  smell. 

FAULTS    IN    EVAPORATING    COILS. 

Faults  in  evaporating  coils  are  very  similar  to  those  in  con- 
denser   pipes.      There    may    be    leaks    at    joints,    allowing    ths 


94  COLD    STORAGE   ON    BOARD    SHIP. 

refrigerant  to  leak  out,  with  the  results  explained,  and  if  the 
evaporator  is  employed  to  cool  brine,  which  is  used  for  the  cold 
chambers,  and  the  system  is  allowed  to  stand  for  a  certain  time 
during  the  day,  and  even  in  some  cases  when  not,  a  small  quan- 
tity of  the  brine  will  probably  work  its  way  into  the  evaporator 
coils,  and  will  give  rise  to  the  troubles  already  described.  With 
ammonia,  a  leak  into  the  brine  tank  is  made  manifest  by  the 
smell  and  a  litmus  paper  test,  and  should  be  immediately  seen  to 
by  pumping  the  refrigerant  out  of  the  evaporator  coils,  emptying 
the  brine  tank,  and  examining  all  joints,  if  necessary,  with  air 
pressure,  as  described. 

Another  source  of  trouble  with  the  evaporator  coils  has 
already  been  alluded  to,  the  deposit  on  the  outside  or  the  inside 
of  the  pipes.  Where  the  evaporator  coils  are  carried  right  into 
the  cold  chamber,  they  very  frequently  become  covered  with  a 
coating  of  ice.  This  should  be  cleared  off  periodically.  Where 
the  evaporator  is  employed  to  cool  brine  in  a  brine  tank,  the 
salts  contained  in  the  brine  are  sometimes  deposited  on  the 
outside  of  the  pipes,  forming  a  crust,  as  explained  in  connection 
with  the  condenser  coils,  which  resists  the  passage  of  the  heat 
from  the  brine  to  the  refrigerant,  with  the  result  that  a  smaller 
quantity  of  work  is  done,  a  smaller  quantity  of  heat  is  lifted  at 
each  stroke  of  the  compressor,  and  either  the  compressor  must 
run  faster,  or  the  temperature  of  the  brine  will  go  up.  The 
same  thing  will  happen  if  there  is  a  deposit  of  oil  or  any  other 
substance  on  the  inside  of  the  evaporator  pipes. 

The  fact  that  the  evaporator  coils  are  working  badly  will  be 
known  by  two  things,  the  temperature  of  the  room  or  the  brine, 
or  the  air  it  is  cooling  will  rise,  and  the  gage  pressure  on  the 
end  of  the  coils  will  also  rise,  because  the  gas  is  not  properly 
expanded  down.  The  remedy  is,  to  examine  the  evaporator 
coils  on  the  outside,  periouically,  and  to  clean  off  any  deposit 
that  is  formed.  This  applies  also  to  the  condenser  coils,  and 
the  cleaning  off  should  be  done  by  means  of  a  brush  which  goes 


TROUBLES    WITH    COMPRESSOR   VALVES.  95 

right  down  into  the  condenser,  or  the  evaporator  tank,  and  gets 
at  every  part  of  each  of  the  pipes  to  be  cleaned. 

Where  the  deposit  is  on  the  inside  of  the  evaporator  coils, 
there  is  only  one  remedy,  disconnection  and  blowing  through 
with  steam  and  air,  as  already  described,  though  the  matter  may 
be  temporarily  put  right  by  increasing  the  speed  of  the  com- 
pressor, where  the  compressor  will  stand  it,  or  by  opening  the 
regulator  valve  widely  where  there  is  a  margin  available.  The 
piston  speed  of  refrigerating  compressors  is  very  low,  usually 
not  more  than  180  feet  per  minute,  and  it  is  not  wise  to  run 
them  faster,  because  it  is  apt  to  lead  to  heating  of  the  com- 
pressor. But  on  occasion  they  may  be  run  slightly  faster,  pro- 
viding that  it  is  done  with  care,  and  where  it  is  a  case  of 
necessity.  When  this  is  done,  however,  the  compressor  should 
be  very  carefully  watched  for  any  heating,  and  anything  of  the 
kind  immediately  attended  to. 

It  may  happen  that  one  or  more  of  the  refrigerator  coils  are 
not  doing  their  work,  and  from  that  cause  the  quantity  of  heat 
taken  out  is  less  than  it  would  be,  approximately  in  proportion 
to  the  number  of  dead  coils.  The  evaporator  coils  that  are  not 
doing  their  work  may  be  known  by  the  absence  of  the  frost  on 
the  coils  themselves,  or  where  they  are  immersed  in  a  brine  tank, 
on  the  short  exposed  piece  of  pipe  leading  to  the  header.  Where 
this  happens,  the  faulty  coils  should  be  temporarily  bridged  over, 
disconnected  from  the  service,  and  examined,  care  being  taken,  in 
the  case  of  ammonia,  to  remove  the  ammonia  either  from  the 
faulty  coils  themselves,  or,  if  that  cannot  be  done,  from  the  whole 
of  the  evaporator  coils,  before  disconnecting, 

TROUBLES    WITH    COMPRESSOR   VALVES. 

Marine  engineers  hardly  need  reminding  that  valves  give 
trouble.  The  compressor  valves,  as  explained  in  the  descriptive 
part  of  these  articles,  are  kept  on' their  seats  by  powerful  springs, 


96  COLD    STORAGE   ON    BOARD    SHIP. 

the  valve  box  either  being  part  of  the  casting  forming  the  end 
of  the  compressor  cylinder,  or  in  some  cases  being  screwed  on 
the  outside.  In  all  cases  there  is  the  usual  valve  rod  moving  in 
and  out  as  the  valve  opens  and  closes,  and  there  is  the  usual 
trouble  that  the  valve  rod  may  be  bent,  or  that  grit  may  get 
between  the  valve  and  its  seat.  In  either  case  leakage  may  re- 
sult; leakage  of  the  suction  valve  meaning  the  expulsion  of  a 
portion  of  the  charge,  in  place  of  its  being  compressed  to  its 
proper  pressure;  and  leaking  of  the  delivery  valve  meaning  a 
reduction  of  the  pressure  at  which  the  gas  is  delivered  to  the 
condenser,  since  there  will  be  a  certain  amount  of  suction,  as  the 
piston  returns  after  the  compression  stroke.  There  is  only  one 
rule  applying  to  this  class  of  fault, — watch  the  working  of  the 
valves,  and  examine  them  as  often  as  convenient.  Usually  their 
proper  action,  or  the  reverse,  may  be  heard. 

There  is  a  more  troublesome  fault  in  connection  with  valves, 
where  the  valve  rod  is  slightly  bent,  and  that  is,  an  intermittent 
sticking.  The  suction  valve  may  not  properly  open  on  one  stroke, 
while  it  may  open  on  another,  and  the  delivery  valve  the  same. 
The  result  of  this  is,  the  action  of  the  compressor  is  irregular, 
and  this  is  shown  by  the  throw  of  the  gages.  Watching  the 
gages,  as  advised  above,  will  in  a  great  many  cases  show  trouble 
in  time. 

The  same  remarks  apply  to  leakage  past  the  piston.  This 
arises  when  the  piston  leathers  are  partly  worn  out,  and  the 
result  is,  the  gas  is  not  compressed  to  its  proper  pressure,  the 
condenser  pressure  falling  and  the  evaporator  pressure  rising. 
Again,  when  this  happens,  make  an  examination  of  valves  and 
piston  at  the  earliest  opportunity,  unless  meanwhile  it  has  been 
shown  that  the  fall  is  due  to  some  other  cause. 

If  either  valves  or  piston  are  suspected  of  leaking,  the  fact 
may  be  ascertained  with  a  fair  amount  of  certainty  by  closing 
the  regulator  valve,  and  continuing  to  run  the  compressor.  As 
the  gas  is  being  gradually  drawn  over  from  the  low  pressure 


TESTING    THE    GAGES.  97 

evaporator  side  to  the  condenser  side,  the  pressure  on  the  evapo- 
rator side  will  gradually  fall,  and  in  a  certain  number  of  revolu- 
tions which  the  manufacturers  will  give  (in  one  case  it  is  200 
revolutions),  the  pressure  will  come  down  about  80  percent — in 
the  case  of  carbonic  acid,  from  25  atmospheres  to  5  atmospheres. 
If  the  pressure  does  not  come  down,  it  is  evident  that  the  gas 
is  leaking  past  the  piston  or  the  valves,  and  they  should  be 
examined. 


TESTING  THE  GAGES. 

Gages,  unfortunately,  sometimes  vary,  even  the  best,  and  when 
carefully  handled,  and  it  may  therefore  happen  that  misleading 
indications  will  be  given.  The  only  way  to  test  the  gages  at 
sea,  or  anywhere  away  from  a  physical  laboratory  to  which  they 
can  be  sent,  is  by  stopping  the  compressor,  opening  all  the  valves, 
and  allowing  the  system  to  settle  down.  The  whole  of  the  re- 
frigerant then  assumes  one  temperature  and  one  pressure,  the 
temperature  of  the  brine  tank,  and  consequently  the  gages  at 
the  condenser  and  at  the  refrigerator  should  indicate  exactly  the 
same.  If  they  do  not,  comparison  should  be  made  between  them, 
and  the  only  thing  that  can  be  done  is  to  bear  in  mind  that  there 
is  this  difference,  and  the  "freezer"  engineer  may  be  guided  in 
reading  the  indications  of  his  gages  by  the  fact  that  they  do  indi- 
cate differently. 

When  it  is  found  that  the  gages  do  not  indicate  alike  the  earli- 
est opportunity  should  be  taken  of  either  changing  gages  or 
having  them  tested.  Gages  of  all  kinds  are  very  difficult  indeed 
to  construct  accurately.  In  the  United  Kingdom,  manufacturers 
keep  standard  test  gages,  which  are  frequently  compared  with 
those  in  service,  and  periodically  sent  to  them  for  comparison 
with  the  standard  instruments  there. 


98  COLD   storage;  on   board   ship. 

FAULTS     IN     THE     BRINE     CIRCULATING     SYSTEM. 

Brine  circulation  is  adopted,  as  explained  in  the  early  part  of 
these  articles,  for  two  reasons.  Where  ammonia  is  the  refriger- 
ant, it  is  a  very  serious  matter  if  any  of  it  escapes  into  the  cold 
chamber,  where  meat  or  other  produce  is  stored.  With  carbonic 
acid  this  difficulty  almost  disappears.  It  quite  disappears  if  a 
proper  system  of  ventilation  is  employed,  so  that  the  air  in  the 
cold  chamber  is  changed,  and  the  vapors  given  off  by  the  produce 
are  carried  away.  In  any  case  it  would  have  to  be  a  somewhat 
large  leak  that  would  cause  any  serious  inconvenience. 

The  other  reason  for  employing  brine,  and  it  is  particularly 
applicable  to  shipboard  work,  is,  that  it  enables  the  engineer  to 
carry  different  holds  or  different  cold  chambers,  at  different 
temperatures,  and  all  from  one  set  or  plant.  The  case  is  by  no 
means  infrequent  where  some  of  the  holds  are  carrying,  say, 
frozen  mutton,  while  one  or  more  of  the  others  are  carrying 
chilled  beef.  Frozen  mutton  may  be  frozen  as  hard  as  you 
please,  and  it  is  only  a  question  of  keeping  the  temperature  low. 
With  chilled  beef  the  matter  is  quite  different.  A  fall  of  tem- 
perature beyond  a  degree  or  two  is  just  as  fatal  as  a  rise  of  tem- 
perature. In  fact,  a  rise  of  several  degrees  of  temperature,  pro- 
viding that  the  subsequent  cooling  does  not  take  place  too  rap- 
idly, will  do  far  less  harm  than  a  fall  of  temperature.  Anything 
in  the  nature  of  freezing,  where  chilled  beef,  fruit,  or  other  sub- 
stances that  must  not  be  frozen  are  carried,  is  fatal. 

With  brine  circulation  the  engineer  is  completely  master  of 
the  situation,  provided  that  his  plant  is  properly  laid  out,  and 
that  it  is  properly  attended  to.  With  this  arrangement,  as  ex- 
plained, the  brine  is  cooled  by  the  evaporator  coils  in  one  or 
more  tanks,  and  the  cooled  brine  is  pumped  to  the  brine  grids  in 
the  different  holds  or  cold  chambers,  where  it  extracts  the  heat, 
returns  to  the  evaporator  tank  at  a  higher  temperature,  delivers 
up  its  heat,  and  commences  its  round  again,  and  so  on. 


FAULTS    IN    THE    BRINE    CIRCULATING     SYSTEM.  99 

Brine  again  is  employed  because  it  has  a  lower  freezing  tem- 
perature than  water.  It  is  hardly  necessary  to  point  out  that  it 
would  be  impossible  to  circulate  water  at  a  temperature  below 
freezing  point,  but  the  addition  of  any  solid  to  water,  providing 
the  solid  is  properly  dissolved,  immediately  lowers  the  freezing 
point.  In  the  case  of  chloride  of  calcium,  which  is  the  substance 
nearly  always  employed,  almost  any  degree  of  temperature  can 
be  carried,  providing  that  the  solution  carries  a  sufficient  per- 
centage of  the  chloride.  With  I  percent  of  chloride  the  freezing 
point  of  the  solution  is  31  degrees  F. ;  with  5  percent  it  is  27^ 
degrees  F. ;  with  10  percent  it  is  22  degrees  F. ;  with  15  percent 
it  is  15  degrees  F. ;  with  20  percent  it  is  5  degrees  F. ;  and  with 
25  percent  it  is  — 8  degrees  F.  From  15  to  20  percent  is  the 
strength  of  solution  usually  carried,  where  freezing  tem- 
peratures are  required,  but  there  is  no  reason  to  carry  this 
strength  of  solution,  where  the  higher  temperatures  are  carried 
for  chilled  beef,    2g]/2  degrees  F.,  and  in  the  neighborhood. 

It  is  a  disadvantage  to  employ  a  too  dense  solution  of  the 
chloride  for  two  reasons.  In  the  first  place,  the  greater  the 
quantity  of  chloride  in  the  solution,  the  lower  is  the  specific  heat. 
With  1  percent  of  chloride  the  specific  heat  of  the  solution  is 
0.996,  practically  the  same  as  water.  With  5  percent  it  has  sunk  to 
0.964;  with  10  percent  to  0.896;  with  15  percent  to  0.860;  with 
20  percent  to  0.834;  and  with  25  percent  to  0.79,  approximately. 
This  means  that  with  a  20  percent  solution,  approximately,  the 
heat  carrying  power  of  a  given  quantity  of  the  solution  is  15 
percent  less  than  that  of  water,  and  this  means  that  a  larger 
quantity  of  the  solution  must  be  circulated  to  carry  off  the 
same  quantity  of  heat  from  the  cold  chamber,  the  air,  etc. 

The  other  disadvantage  is,  the  greater  the  density  of  the  solu- 
tion, the  greater  the  tendency  to  deposit  on  the  pipes  in  which 
the  solution  is  circulating,  and  on  the  evaporator  pipes,  in  the 
evaporator  tank.    And  this  leads  to  one  of  the  possible  faults. 

As  in  all  these  cases,  there  are  two  possible  sources  of  failure, 


100  COLD    STORAGE    ON     BOARD     SHIP. 

leakage  and  obstruction.  If  the  joints  of  the  brine  pipe  leak, 
there  is  not  the  same  quantity  of  brine  circulating,  and  therefore 
there  is  not  the  same  quantity  of  heat  carried  off.  This  trouble 
is  very  easily  located,  and  the  marine  engineer  can  be  trusted 
to  grapple  with  it  without  difficulty.  But  the  other  possible 
source  of  trouble,  the  obstruction,  is  very  much  more  serious, 
very  much  more  difficult  to  discover,  and  very  much  more  diffi- 
cult to  put  right.  The  same  rule  applies  in  this  case  that  has 
been  given  in  connection  with  the  compressor,  and  so  on,  "watch 
the  gages."  In  this  case  the  gages  are  the  thermometers.  When 
everything  is  working  properly  there  will  be  a  certain  difference 
of  temperature  between  the  ingoing  brine  and  the  outgoing  brine, 
from  any  given  cold  chamber.  If  there  is  an  alteration  in  these 
quantities,  if  the  incoming  brine  is  at  a  higher  temperature  than 
it  should  be  to  produce  the  proper  extraction  of  heat,  the  fault 
is  to  be  found  probably  in  the  evaporator  tank.  The  heat  is  not 
being  properly  extracted  from  the  returning  brine,  and  there- 
fore it  is  not  setting  out  at  the  low  temperature  it  should  have. 
The  evaporator  coils  may  not  be  doing  their  work  properly,  as 
described  in  the  previous  notes,  or  again,  there  may  be  a  deposit 
on  the  inside  of  the  brine  pipes,  which  is  preventing  the  heat 
from  being  extracted  from  the  brine,  as  mentioned  several  times 
above. 

Another  possible  cause  of  trouble  with  brine  circulation  arises 
when  the  brine  is  not  sufficiently  strong  to  withstand  the  low 
temperature  of  the  evaporator  tank.  It  will  be  understood  that 
this  is  the  other  side  of  the  question.  As  explained,  the  solution 
must  not  be  too  strong,  for  the  reasons  named.  It  also  must  not  be 
£o  weak  that  in  passing  through  any  part  of  the  system,  say  the 
evaporator  coils,  even  a  small  portion  of  it  will  freeze.  When 
this  happens  there  is  a  formation  of  ice  upon  the  outside  of  the 
evaporator  coils,  and  this  ice  has  the  same  effect,  to  a  certain 
extent,  in  preventing  the  passage  of  heat  from  the  brine  to  the 
refrigerant,  as  the  deposit  of  the  salt  would. 


FAULTS  IN   THE  BRINE  CIRCULATING   SYSTEM.  101 

The  methods  adopted  where  brine  circulation  is  employed,  with 
frozen  produce,  and  with  chilled  produce,  are  sometimes  quite 
different.  It  is  evident  that  with  frozen  produce,  all  that  is  nec- 
essary being  to  maintain  the  temperature  below  a  certain  figure 
during  the  whole  twenty-four  hours,  if  a  store  of  cold  is  pro- 
vided in  the  hold  or  cold  chamber,  in  the  shape  of  a  quantity  of 
brine  whose  temperature  is  reduced  to  a  certain  figure,  the  plant 
may  be  worked  for  only  a  certain  number  of  hours  a  day,  the 
store  being  maintained  at  its  temperature  for  the  remainder  of 
the  time  by  drawing  upon  the  reserve  of  cold  in  the  brine  store. 
This  plan  has  a  great  deal  to  recommend  it,  and  is  often  employed 
on  shore.  It  has  one  obvious  advantage,  in  that  it  allows  of  a 
smaller  staff  being  employed.  One  "freezer"  engineer,  and  per- 
haps a  greaser,  can  run  the  plant  for,  say,  a  couple  of  watches 
during  the  day,  get  the  brine  to  its  temperature,  and  allow  it  to 
look  after  itself,  with  an  occasional  look  at  the  thermometers, 
for  the  remainder  of  the  twenty-four  hours.  The  only  thing 
necessary,  and  it  involves  only  a  very  simple  calculation,  is  that 
there  shall  be  a  sufficient  quantity  of  brine,  held  at  a  sufficiently 
low  temperature,  to  provide  the  necessary  cold  for  the  sixteen 
or  eighteen  hours  during  which  the  plant  is  not  working.  From 
the  figures  given  for  the  specific  heat  of  the  brine  solution,  the 
above  calculation  is  easily  made  for  a  given  size  of  hold  or  cold 
chamber,  with  a  given  quantity  of  produce  stored  in  it. 

With  chilled  meat,  fruit,  or  produce  which  must  not  be  frozen, 
and  the  temperature  of  which  must  not  vary  more  than  a  very 
few  degrees,  it  is  necessary  to  run  the  plant  continuously  during 
the  whole  twenty- four  hours;  and  further,  the  rise  of  tempera- 
ture in  the  brine  supplying  the  hold  in  which  the  chilled  beef  or 
fruit  is  held  should  be  allowed  to  be  only  a  very  few  degrees 
between  the  inlet  and  outlet.  Again,  the  temperatures  on  the 
inlet  and  outlet  pipe  of  each  hold  and  of  each  portion  of  each 
hold,  will  be  a  guide  to  the  "freezer"  engineer,  as  to  what  is 
going  on  inside  the  hold,  or  that  portion  of  the  hold.     If  the 


102  COED    STORAGE    ON     BOARD    SHIP. 

temperature  on  the  outlet  is  higher  than  proper  working  shows 
is  best,  evidently  more  heat  from  some  cause  is  being  given  off 
inside,  and  it  would  probably  be  wise  to  deliver  a  larger  quantity 
of  the  brine  to  that  hold  or  that  portion  of  the  hold.  On  the 
other  hand,  if  the  temperature  at  the  outlet  is  lower  than  the 
normal,  it  shows  that  there  is  very  little  difference  in  temperature 
between  the  brine  and  the  air  in  that  portion  of  the  hold,  and 
as  this  may  mean  that  the  temperature  there  is  lower,  or  may 
become  lower  than  it  should  be,  the  quantity  of  brine  passing  is 
lessened.  This  is  done,  of  course,  by  means  of  the  circulating 
pumps,  and  by  the  valves  on  the  pipes  and  headers. 

It  will  be  wise,  in  the  case  of  chilled  meat  and  fruit,  to  check 
the  indications  of  the  thermometers  in  the  brine,  by  thermome- 
ters in  the  stores  themselves,  and,  for  this  purpose,  thermometers 
arranged  to  indicate  the  temperature  inside  on  some  apparatus 
outside  are  of  great  service.  There  are  several  forms  of  elec- 
trical apparatus  on  the  market  which  will  accomplish  this.  In 
particular,  there  is  a  series  of  instruments  made  by  the  Cam- 
bridge Scientific  Instrument  Company,  of  Cambridge,  England, 
and,  the  writer  believes  also,  by  firms  in  America,  in  which  the 
variation  in  the  resistance  of  a  platinum  wire  is  made  to  show 
the  temperature  tale  inside  of  a  cold  store,  at  an  indicating  or 
testing  board,  on  the  outside  in  the  engineer's  room,  or  in  any 
other  convenient  position. 

The  rationale  of  the  arrangement  is,  the  electrical  resistance 
of  all  metals  increases  with  a  rise  in  temperature,  and  decreases 
with  a  fall  in  temperature,  in  a  certain  definite  proportion,  for 
each  degree  of  rise  or  fall.  If,  therefore,  an  electric  circuit  is 
formed,  including  a  small  piece  of  platinum  wire,  a  source  of 
current  and  an  electrical  indicating  apparatus  (it  may  be  a  gal- 
vanometer, calibrated  in  degrees  F.  or  C,  the  platinum  wires 
being  fixed  upon  the  tubes  arranged  to  be  placed  in  the  cold 
store,  and  the  connecting  wires  being  led  through  insulated  tubes 
in  the  walls  of  the  store  to  the  indicating  apparatus),  every  rise 


PREPARING    THE    BRINE    SOLUTION.  103 

and  fall  of  temperature  will  be  seen  at  the  indicating  point,  and 
may  also  be  recorded  upon  a  chart,  in  a  manner  similar  to 
barometric  and  other  records. 

There  are  other  arrangements  worked  electrically,  in  which  a 
rise  of  temperature  of  a  certain  number  of  degrees  closes  an 
electric  circuit  and  drops  an  indicator  in  the  engineer's  room; 
a  fall  of  temperature  of  a  certain  number  of  degrees  closing 
another  circuit,  and  dropping  another  indicator,  and  so  on.  But 
the  electrical  thermometer,  giving  its  own  records  upon  a  dial 
or  chart,  is,  in  the  writer's  opinion,  far  preferable. 

It  has  one  disadvantage,  especially  for  seagoing  work — it  is 
necessarily  delicate;  but  it  is  perfectly  possible  to  protect  the 
platinum  wire  in  such  a  manner  that  even  the  knocking  about  in 
a  very  heavy  seaway  will  not  easily  damage  it,  and  the  sure 
indications  the  thermometers  give  are  worth  a  great  deal  of 
trouble  to  obtain,  where  such  important  results  follow,  as  in  the 
case  of  a  variation  of  temperature  with  chilled  meat,  fruit,  etc. 
With  such  a  set  of  thermometers,  and  a  careful  attendant  con- 
stantly watching  the  thermometers  on  the  brine  pipes  and  in  the 
cold  stores,  it  should,  in  the  writer's  opinion,  be  perfectly  practi- 
cable to  carry  chilled  meat,  fruit,  etc.,  for  long  voyages,  six  weeks 
or  more,  providing  that  the  other  points  that  have  been  men- 
tioned in  connection  with  the  operation  of  the  plant  are  attended 
to. 

PREPARING   THE   BRINE   SOLUTION. 

Tt  is  very  important  indeed  that  the  brine  solution  should  be 
carefully  prepared.  It  is  not  sufficient  to  take  a  tub  of  water 
and  throw  some  calcium  chloride  into  it,  and  allow  it  to  dissolve. 
A  certain  definite  quantity  of  the  calcium  chloride  should  be  dis- 
solved, in  a  certain  definite  quantity  of  water,  and  the  purest 
water,  distilled  if  possible,  should  be  employed.  On  no  account 
should  sea  water  be  employed,  either  as  a  solvent  for  the  calcium 
chloride,  or  to  take  its  place.     A  brine  is  made  from  common 


104  COLD  storage;  on   board  ship. 

salt  which  answers  all  the  requirements  of  a  brine  solution,  if 
made  in  the  proper  strength,  according  to  the  temperature  to 
which  it  has  to  be  subject;  but  it  is  not  wise  to  employ  a  salt 
brine  solution,  if  calcium  chloride  can  be  obtained. 

The  reason  is  one  that  will  be  very  familiar  to  marine  engi- 
neers. Common  salt  acts  chemically  upon  almost  every  metal 
with  which  it  comes  in  contact,  and  particularly  upon  iron,  while 
calcium  chloride  has  practically  no  action  upon  iron,  as  long  as 
it  is  pure.  Where  calcium  chloride  is  employed,  it  is  much  better 
to  use  plain  iron  pipes  than  galvanized  iron.  Calcium  chloride 
acts  chemically  upon  zinc,  with  a  liberation  of  hydrogen,  and 
sometimes  consequent  troubles. 

If  the  engineer  is  obliged  to  employ  any  salt  for  his  solution, 
owing  to  his  being  in  a  port  where  calcium  chloride  is  unobtain- 
able, the  following  are  the  figures  he  has  to  work  to :  With  i  per- 
cent of  common  salt  the  freezing  point  of  the  solution  is  30^2 
degrees  F. ;  with  5  percent  it  is  25  degrees  F. ;  with  10  percent 
it  is  18  degrees  F. ;  with  20  percent  it  is  6  degrees  F. ;  and  with 
25  percent  5  degrees  F.  It  will  be  seen  that  the  freezing  points 
are  a  little  under  those  of  the  solution  of  calcium  chloride.  The 
specific  heats  are  as  follows:  With  1  percent,  0.992;  with  5  per- 
cent, 0.960 ;  with  10  percent,  0.892;  with  20  percent,  0.829;  and 
with  25  percent,  0.783,  about.  There  is  very  little  difference 
again  between  the  specific  heats,  though  calcium  chloride  has 
slightly  the  advantage.  If  common  salt  is  employed  temporarily, 
as  a  brine  solution,  it  should  be  made  only  with  pure  distilled 
water,  or  if  distilled  water  is  not  obtainable,  the  purest  water 
that  can  be  had.  Fresh  water  in  any  case,  and  the  earliest 
possible  return  to  the  use  of  calcium  chloride,  should  be 
made,  the  brine  pipes  being  thoroughly  washed  out  before 
the  calcium  chloride  is  admitted  into  them. 

Tn  preparing  either  the  calcium  chloride  or  the  common 
salt  solution,  the  best  plan  is  to  hold  the  salt  either  in  a  bucket 
with  perforations,  or  in  a  cage,  or  something  similar,  weighing 


PREPARING    THE    BRINE     SOLUTION.  105 

the  proper  quantity  of  the  salt  for  a  definite  quantity  of 
solution  into  the  bucket  or  cage,  and  then  either  immersing  the 
whole  in  a  vessel  containing  the  definite  quantity  of  water  to 
make  the  proper  density  of  solution,  or  purrping  the  water  in 
over  the  cage  into  a  vessel  arranged  to  hold  it,  and  allowing 
the  whole  to  settle,  etc. 

There  is  another  point  which  ought  to  be  mentioned.  Com- 
mercial calcium  chloride  too  often  contains  impurities,  even  as 
much  as  25  percent  of  common  salt,  and  if  a  solution  is  made 
up  from  this  substance,  chemical  actions  will  take  place 
between  the  calcium  chloride  and  the  common  salt,  leading  to 
a  reduction  in  the  efficiency  of  the  system.  That  is  to  say, 
a  definite  quantity  of  a  given  solution,  passing  through  a  cold 
chamber  in  a  given  time,  the  liquid  having  been  cooled  to  a 
given  temperature,  will  not  absorb  the  same  quantity  of  heat 
as  the  pure  solution  of  calcium  chloride  or  sodium  chloride 
would  have  done.  In  addition  to  this,  in  working,  the  sodium 
chloride,  being  less  soluble  than  the  calcium  chloride,  is  apt 
to  somewhat  freely  deposit  on  the  inside  of  the  pipes,  with 
the  results  that  have  been  mentioned.  When  buying  calcium 
chloride,  therefore,  it  is  wise  to  test  it,  and  the  best  test  is, 
by  making  a  small  quantity  of  solution,  of  a  definite  density, 
and  taking  its  freezing  point.  That  is  to  say,  freezing  it,  as  can 
easily  be  done  where  there  is  a  refrigerating  plant  on  the 
ground,  and  taking  the  freezing  point  with  a  thermometer. 

Calcium  chloride  and  sodium  chloride  are  very  much  alike 
in  appearance,  and,  in  addition,  commercial  calcium  chloride  con- 
tains, on  an  average,  25  percent  of  water,  and  will  absorb  from 
half  to  nearly  all  its  own  weight  of  water  when  the  conditions 
are  favorable.  In  America  the  calcium  chloride,  in  its  com- 
mercial form,  comes  from  the  makers  in  a  solid  cake  inclosed 
in  air-tight  thin  iron  drums.  Before  use,  it  has  to  be  broken  up 
into  lumps,  the  lumps  being  put  into  the  cage  or  bucket,  as 
explained. 


106  COLD    STORAGE    ON    BOARD    SHIP. 

FAULTS   IN   AIR  COOLED  PLANTS. 

The  principal  points  to  be  looked  out  for  in  connection  with 
air  cooled  plants  are  the  condition  of  the  air  ducts,  and  the 
temperature  in  different  parts  of  the  hold.  Dust  and  dirt  of 
various  kinds  sometimes  collect  in  the  air  ducts,  and  may  be 
carried  into  the  cold  chamber,  if  not  removed.  The  "freezer" 
engineer  should  examine  the  ducts  as  frequently  as  possible, 
particularly  after  bad  weather,  when  everything  has  been 
strained,  and  when  dust  will  have  been  created  to  a  certain 
extent,  when  everything  is  more  or  less  upside  down ;  and 
should  have  all  dust,  and  anything  that  can  be  carried  into  the 
cold  chamber,  removed. 

The'  question  of  the  distribution  of  temperature  within  the 
chamber  is  also  an  exceedingly  important  one,  and  the  engi- 
neer should  give  it  considerable  attention.  The  ports  in  the 
ducts  should  be  so  arranged  that  air  currents  can  be  sent 
through  every  part  of  the  chamber,  and  the  fruit  or  other 
produce  that  is  air  cooled  should  be  so  arranged  that  the  air 
penetrates  to  all  parts.  The  engineer  should  look  into  this 
matter  also  after  heavy  weather.  Bananas,  crates  of  rabbits, 
fruits  of  all  kinds,  that  are  air  cooled,  should  be  arranged  with 
an  air  space  all  around  them.  They  should  not  rest  on  the 
floor,  for  instance,  but  should  be  supported  on  laths,  or  any- 
thing that  will  allow  a  current  of  air  to  pass  under  them,  and 
they  should  not  be  stacked  closely  together,  for  the  same  rea- 
son. If  they  have  been  thrown  together  during  heavy  weather, 
they  should  be  replaced  as  soon  as  it  is  possible  to  do  any- 
thing within  the   cold  chamber. 

There  is  great  danger,  in  air  cooled  chambers,  of  the  currents 
of  air  passing  across  from  the  port  of  the  inlet  duct  to  the  port 
of  the  outlet  duct,  and  largely  avoiding  a  portion  of  the  pro- 
duce. This  will  be  especially  the  case  if  there  are  corners  in 
the  hold  or  cold  chamber,  in  which  a  portion  of  the  produce  is 


FAULTS  IN  AIR  COOLED  PLANTS.  IOJ 

stored,  and  to  which  it  is  difficult  for  the  air  to  penetrate.  A 
very  liberal  supply  of  thermometers  will  inform  the  engineer 
as  to  the  temperature,  and  for  this  purpose,  though  the  elec- 
trical thermometers  described  in  a  previous  note  are  much 
better,  and  will  give  him  the  information  he  wants  without  his 
entering  the  hold,  he  can  still  obtain  quite  reliable  information 
from  a  number  of  cheap  thermometers,  providing  that  he 
knows  each  individual  instrument. 

Very  few  thermometers,  as  already  explained,  agree.  The 
methods  of  constructing  thermometers  vary  considerably,  and 
the  ordinary  method  also  varies  in  toto  from  what  is  supposed 
to  be  the  theory  of  the  subject,  the  theory  unfortunately,  as  often 
happens,  being  wrong.  But  it  is  an  easy  matter  to  compare  indi- 
vidual thermometers,  with  one  thermometer  that  is  known  to  be 
fairly  accurate,  and  even  where  this  is  not  possible,  to  obtain  a 
sufficient  guidance  by  the  readings  of  thermometers  that  are  not 
themselves  at  all  accurate,  providing  that  they  always  read  the 
same  number  of  degrees,  for  the  same  temperature.  Thus  the 
"freezer"  engineer  will  be  able  to  judge  when  his  fruit  or  other 
produce  is  all  right,  and  is  keeping  so,  and  he  can  mark  that  on 
a  thermometer,  and  it  will  not  matter  whether  the  thermometer 
is  really  registering  the  correct  temperature  or  not — the  figure, 
whatever  it  may  be,  will  be  his  guide  to  work  to. 

If  the  engineer  finds  that  the  temperature  rises  or  falls  unduly, 
(both  are  bad,  as  already  explained)  in  any  part  of  the  hold  or 
cold  chamber,  he  must  alter  the  current  of  air,  either  by  means 
of  the  ports  in  the  air  ducts,  by  introducing  fans,  or  by  putting 
t  p  temporary  partitions,  of  board  or  sail  cloth,  just  as  mining 
r:cn  do,  to  direct  air  currents  into  particular  working  places.  In 
any  case  he  must  direct  more  air  into  any  corner,  or  any  part 
where  the  temperature  unduly  rises,  and  he  must  divert  air  from 
any  part  where  it  unduly  falls. 

Another  point  in  connection  with  air  cooled  chambers  is  the 
direction  of  the  air.     This,  it  will  be  seen,  is  a  most  important 


108  COU)  STORAGE  ON  BOARD  SHIP. 

matter,  and  it  is  not  always  easy  to  determine  the  direction  of 
the  air.  The  little  apparatus  called  the  anemometer,  which  is  the 
correct  apparatus  for  measuring  the  velocity  of  air  currents,  and 
therefore  of  the  strength  of  air  currents  in  different  parts  of  a 
chamber,  is  very  delicate,  and  requires  a  certain  amount  of  skill 
in  handling.  Equally  as  good  an  apparatus  is  one  of  the  toys 
that  are  made  for  children,  consisting  of  light  vanes  made  of 
paper,  or  any  light  material,  held  very  loosely  on  a  pin  at  the  end 
of  a  stick.  The  apparatus  looks  like  a  childish  one,  but  it  is 
very  useful  for  measuring  the  direction  and  the  strength  of  air 
currents.  It  is  an  apparatus  that  any  engineer  can  make  up 
quickly  for  himself,  at  practically  no  cost  beyond  the  time  in- 
volved; and  by  having  several  of  these  fixed  in  different  parts 
of  the  hold  he  may  see  at  a  glance,  from  one  of  the  duct  ports, 
how  the  air  currents  are  going  within  the  hold,  and  he  can  also, 
by  constructing  them  of  slightly  varying  size  and  form,  obtain 
some  very  useful  and  reliable  information. 

Every  engineer  knows  that  in  practical  work,  what  is  required 
is,  not  so  much  absolute  measurement,  as  relative  measurement. 
We  do  not  trouble  our  heads  about  the  absolute  steam  pressure, 
nor  the  absolute  temperature.  What  we  do  trouble  about  is, 
whether  the  pressure  or  the  temperature  rises  or  falls  above 
certain  figures  that  we  are  working  to.  Similarly,  we  do  not 
want  to  know  the  accurate  velocity  of  the  air  passing  through  a 
cold  chamber,  but  we  do  want  to  know  the  relative  velocity  pass- 
ing in  different  parts  of  the  chamber,  and  that,  these  little  pieces 
of  apparatus  will  tell  us.  The  revolving  paper  vanes  should  be 
made  something  on  the  lines  of  the  vanes  of  the  Blackman's  fan, 
to  be  effective.  They  should  hold  a  certain  amount  of  air  in  a 
sort  of  bag  formation. 

Another  useful  arrangement  is  a  piece  of  very  light  dry  ribbon 
held  on  the  end  of  a  stick.  It  is  also  a  primitive  arrangement, 
but  one  that  is  very  easily  fitted  up,  and  very  useful  where  the 
little  revolving  paper  vanes  are  not  available. 


FAULTS  IN  AIR  COOLED  PLANTS.  109 

It  is  not  necessary  to  repeat  the  instructions  that  have  been 
given  with  regard  to  the  air  cooling  plant  itself.  On  board  ship 
it  can  take  only  one  form,  except  in  very  special  cases,  viz.,  a 
stack  or  grid  of  pipes  through  which  the  refrigerant  passes,  and 
in  which  it  evaporates,  the  air  to  be  delivered  to  the  cold  cham- 
ber being  driven  over  the  surface  of  the  pipes  by  the  aid  of  a 
fan.  If  the  temperature  in  the  hold  rises  unduly,  or  falls  unduly, 
as  a  whole,  not  in  any  particular  part,  the  air  is  either  being 
cooled  too  much  or  it  is  being  driven  at  too  great  a  velocity 
through  the  cold  chamber. 

The  engineer  in  this  case  has  two  methods  of  regulating.  He 
can  either  increase  or  decrease  the  speed  of  the  fan,  increasing 
or  decreasing  the  velocity  of  the  air  current,  thereby  lowering  or 
raising  the  temperature  of  the  air  in  the  hold,  since  every  cubic 
foot  of  air  passing  through  it  at  a  certain  temperature  carries 
off  a  certain  quantity  of  heat;  or  he  can  raise  or  lower  the 
quantity  of  the  refrigerant  passing  into  the  evaporator  coils, 
this  being  accomplished  by  opening  or  closing  the  regulator 
valve. 

There  may  be  the  same  troubles  in  connection  with  an  air 
cooled  plant  as  with  brine  cooling.  The  inside  of  the  evaporator 
coils  ma}'  receive  a  deposit  of  grease  or  other  foreign  matter, 
thus  increasing  the  thermal  resistance  between  the  refrigerant 
and  the  air,  and  leading  to  the  temperature  of  the  air  not  being 
lowered  as  much  as  it  should  be.  And  again,  certain  portions 
of  the  evaporator  coils  may  not  be  doing  their  work,  from 
causes  already  mentioned,  such  as  pipes  having  been  clogged,  or 
a  leak  having  occurred.  In  such  a  case  the  temperature  of  the 
hold  will  rise,  and  it  will  be  necessary,  either  to  increase  the 
quantity  of  refrigerant  passing  into  the  evaporator  coils,  or  to 
increase  the  velocity  of  the  air.  The  fan  in  this  case  is  usually 
electrically  driven,  and  there  should  be  an  arrangement  enabling 
the  speed  of  the  fan  to  be  regulated  within  certain  limits,  as  much 
as  from  one  to  ten,  so  that  probably  increasing  or  decreasing  the 


110  COLD    STORAGE   ON    BOARD    SHIP. 

air  current  will  be  found  a  very  convenient  method  of  regulating 
the  temperature  in  an  air  cooled  hold. 

Where  a  compressed  air  plant  is  employed,  the  air  from  the 
cold  chamber  being  drawn  into  the  compressor,  compressed, 
cooled,  expanded  and  redelivered  to  the  chamber,  there  are  two 
important  points  to  be  attended  to.  The  apparatus,  whatever  it 
may  be,  for  cooling  and  drying  the  air,  directly  after  it  leaves 
the  compressor,  should  be  kept  in  proper  working  order.  It 
usually  consists  of  some  arrangement  in  which  the  air  passes  up- 
wards over  a  number  of  broken  surfaces,  such  as  a  number  of 
glass  marbles,  this  being  one  form  used  by  a  London  firm,  and 
meeting  a  current  of  cold  water  passing  down  over  the  same  sur- 
faces. The  arrangement  is  exactly  the  same  as  that  employed  in 
cooling  towers  on  shore.  The  apparatus,  in  this  case,  performs 
the  double  office  of  partially  cooling  the  air  which  has  been 
heated  in  the  compression  cylinder,  and  of  removing  the  moisture 
which  has  been  brought  over  from  the  cold  chamber,  the  moist- 
ure being  removed  by  the  fact  of  cooling,  and  by  the  production 
of  a  difference  between  the  vapor  tension  of  the  air  and  that  of 
the  cooling  water. 

If  the  temperature  of  the  cooling  water  rises,  as  when  the  ship 
passes  into  the  tropics,  it  is  evident  that  the  same  quantity  of 
water  passing  will  not  effect  the  same  cooling.  It  is  of  the  very 
highest  importance  that  the  air  should  be  cooled  down  as  much 
as  possible,  before  it  passes  into  the  expansion  chamber,  where 
the  principal  cooling  takes  place,  and  also  that  the  moisture  shall 
all  be  removed  from  it,  as  far  as  possible,  for  the  reason  that  if 
there  is  any  moisture  present,  it  will  tend  to  freeze  within  the 
evaporating  cylinder,  and  in  the  delivery  ports  from  the  evapo- 
rating cylinder,  and  so  on.  The  engineer,  therefore,  who  is  in 
charge  of  a  compressed  air  plant,  will  be  wise  to  "freeze"  his 
attention  on  the  air  drying  apparatus.  With  compressed  air,  also, 
there  is  the  great  danger  of  leakage  of  heat  into  the  duct  leading 
from  the  evaporating  cylinder  to  the  cold  chamber,  and  into  the 


FAULTS    IN    COLD   CHAMBERS.  Ill 

ducts  that  distribute  the  cold  air.  There  is  only  one  method  of 
overcoming  this,  and  that  is,  by  maintaining  the  insulation  intact, 
and  there  is  only  one  method  of  ascertaining  whether  anything 
of  the  kind  does  take  place,  and  that  is,  by  observing  tempera- 
tures everywhere. 

FAULTS   IN   COLD    CHAMBERS. 

Faults  in  cold  chambers,  cooled  by  means  of  brine  or  expansion 
coils,  are  of  very  much  the  same  kind  as  those  mentioned  in  con- 
nection with  air  cooled  chambers,  and  the  ducts  of  compressed 
air.  The  great  source  of  trouble  with  cold  chambers  is  the  low- 
ering of  the  insulation  of  the  chamber  itself.  It  has  been  ex- 
plained, in  the  early  part  of  these  articles,  that  there  is  no  such 
thing  as  a  perfect  insulator  for  heat.  Heat  always  passes  through 
the  most  perfect  insulating  wall  that  has  yet  been  devised,  and 
at  a  certain  rate ;  and  the  cold  storage  plant,  the  compressor,  con- 
denser, evaporator,  etc.,  are  designed  to  remove  the  heat  that 
passes  through  the  insulating  walls,  as  it  passes  through,  and  to 
deliver  it  continuously  to  the  cooling  water  of  the  condenser. 

So  long  as  the  insulation  remains  at  a  certain  figure,  that  is  to 
say,  so  long  as  heat  passes  through  the  walls,  floor  and  ceiling  at 
a  certain  definite  rate,  and  so  long  as  the  plant  itself  is  working 
normally,  the  heat  passing  into  the  chamber  is  continually  carried 
away,  a  certain  number  of  heat  units  being  carried  off  at  each 
stroke  of  the  compressor.  If,  however,  the  insulation  fails,  an 
increased  quantity  of  heat  passes  into  the  chamber,  and  unless 
the  evaporator  or  the  brine  coils  carry  off  the  increased  quan- 
tity, the  temperature  will  rise. 

Again,  the  engineer  will  be  wise  to  watch  his  temperatures  by 
any  means  in  his  power,  by  the  aid  of  electrical  thermometers 
if  possible,  but  in  any  case  by  the  aid  of  any  thermometers  that 
he  can  obtain.  If  he  finds  the  temperature  of  his  cold  store 
rising,  he  should  first  ascertain  whether  the  plant  is  working  all 


112  COU)  STORAGE  ON  BOARD  SHIP. 

right.  It  may  be  taken  as  an  axiom  that  in  all  work  of  this 
kind,  where  testing  for  faults  is  necessary,  the  engineer  should 
commence  at  the  very  beginning.  He  should  commence  at  the 
compressor,  see  if  that  is  in  the  condition  described,  see  if  the 
condenser  and  evaporator  gages  are  recording  as  they  ought,  see 
if  the  delivery  pipe  is  in  the  condition  it  should  be.  If  all  these 
things  are  right,  and  the  temperature  goes  up,  it  will  probablv 
be  accompanied  by  a  fall  in  the  pressure  at  the  evaporator  gage, 
since  the  system  will  be  endeavoring  to  do  more  work.  With 
brine  cooling,  the  engineer  has  then  two  methods  of  dealing  with 
the  problem.  He  can  increase  the  velocity  of  the  brine  circula- 
tion, by  increasing  the  speed  of  the  pump,  or  opening  the  valve 
of  a  particular  brine  pipe,  or  he  can  increase  the  quantity  of  the 
refrigerant  passing  into  the  evaporator  coils,  where  the  trouble 
is  common  to  all.  He  will  be  guided  by  circumstances  as  to 
which  course  he  takes.  In  some  cases  it  may  be  easier  and 
simpler  to  slightly  increase  the  speed  of  the  pump.  In  cases 
where  a  pump  runs  at  a  constant  speed  he  cannot  do  this,  and  he 
must  increase  the  quantity  of  the  refrigerant. 

In  the  case  of  chilled  meat,  where  it  is  so  important,  as  ex- 
plained, to  maintain  the  temperature  within  a  few  degrees  of  a 
certain  figure,  neither  going  up  nor  down,  if  the  engineer  finds  his 
temperature  going  down,  probably  his  best  method  of  dealing 
with  the  question  will  be  decreasing  the  velocity  of  the  brine 
circulation  in  the  particular  chamber,  by  closing  the  valve  par- 
tially. Where  there  is  more  than  one  hold  or  cold  chamber  sup- 
plied with  brine  coils,  the  matter  is  regulated  simply  by  altering 
the  valves  on  each  branch  of  the  system. 

RECEIVING    MEAT  AND    PRODUCE. 

Meat  that  is  to  be  carried  frozen  is  usually  frozen  as  soon  as  it 
has  been  killed,  at  the  station  where  it  has  been  grown,  and  is,  or 
should  be,  carried  in  refrigerating  cars  to  the  ship's  side.    Where, 


RECEIVING    MEAT    AND    PRODUCE.  113 

however,  this  is  not  done,  or  where  meat  is  received  newly 
killed,  to  be  placed  in  cold  store,  and  where  it  is  to  be  held 
frozen,  or  chilled,  it  should  on  no  account  be  exposed  to  a  very 
low  temperature  for  some  time  after  it  has  been  killed.  What  is 
known  as  the  animal  heat  should  always  be  allowed  to  get  out  of 
the  meat,  by  radiation,  before  any  cooling  is  attempted.  The 
time  occupied  in  getting  rid  of  the  animal  heat  varies  consider- 
ably. Where  times  presses,  and  where  it  is  not  of  such  a  great 
importance — say  where  the  meat  will  not  have  to  be  kept  for  a 
long  time,  as  when  it  is  intended  for  the  use  of  the  ship's  com- 
pany or  passengers — the  meat  should  be  allowed  to  hang  in  the 
ordinary  temperature  as  long  as  possible,  and  then  it  should  be 
submitted  to  a  gradually  lowering  temperature,  the  heat  being 
slowly  extracted  from  it  in  this  way,  until  finally  it  is  frozen  or 
chilled,  as  required. 

Meat  received  in  this  way  should  on  no  account  be  allowed  to  lie 
on  the  floor,  nor  to  touch  the  walls  or  the  ceiling.  In  ships  which 
carry  chilled  meat,  it  is  usual  to  suspend  carcasses  or  quarters  by 
hooks  arranged  for  the  purpose  below  the  ceiling,  and  in  such  a 
manner  that  the  air  has  free  access  to  every  part  of  the  carcass. 
Where  this  cannot  be  done,  where  it  is  necessary  to  lay  the  meat 
on  something,  battens  or  gratings,  or  something  similar,  should 
be  laid  on  the  floor  of  the  cold  chamber,  and  the  meat  laid  on 
them,  being  so  arranged  that  the  air  has  a  clear  passage  under 
the  meat,  over  it  and  all  around  it ;  and  if  it  is  necessary  to  lay  the 
meat  in  tiers,  successive  tiers  of  battens  should  be  provided,  ful- 
filling the  same  conditions.  The  same  remarks  apply  to  crates  of 
rabbits  and  similar  produce.  Rabbits  are  packed  loosely  in  small 
open  crates,  giving  clear  passage  of  air  through  them,  and  these 
should  be  placed  a  little  off  the  ground,  and  if  obliged  to  be 
stacked  one  above  the  other,  should  be  arranged  by  means  of 
battens  with  air  spaces  between  them.  It  is  particularly  import- 
ant in  the  case  of  chilled  meat,  that  the  cooling  should  be  per- 
formed very  gradually  indeed. 


114  COLD    STORAGE    ON    BOARD    SHIP. 

If  the  meat  on  the  outer  surface  is  frozen  first,  or  even  if  its 
temperature  is  very  much  reduced  before  that  of  the  inner  por- 
tions, it  is  very  liable  to  lead  to  what  is  known  as' "bone  stink." 
In  plain  terms,  the  inner  portion  of  the  meat  sets  up  organic 
chemical  action,  and  rots.  When  this  does  not  actually  occur, 
a  lesser  evil  may  be  met — the  minute  cells  and  vessels  of  which 
the  muscular  portions,  the  eating  portions  of  meat,  are  composed, 
sometimes  burst,  and  the  juices  they  contain  are  lost,  with  the 
result  that  the  meat  so  preserved,  when  it  comes  to  be  cooked,  is 
found  to  have  no  gravy,  and  very  little  flavor,  and  is  consequently 
sold  for  a  very  low  price. 

THAWING   OUT. 

It  will  usually  not  be  within  the  province  of  the  "freezer"  en- 
gineer to  thaw  out  meat,  except  for  the  use  of  the  ship's  com- 
pany or  passengers.  When  he  has  to  perform  this  work,  how- 
ever, it  cannot  be  too  carefully  done  nor  too  gradually.  The  meat 
to  be  thawed  should  be  removed  from  the  cold  chamber  to  one 
only  a  little  higher  in  temperature,  or  arrangements  should  be 
made  to  slightly  increase  the  temperature  of  that  portion  of  the 
chamber  in  which  the  meat  to  be  thawed  out  is  placed.  This 
may  be  accomplished  by  the  aid  of  temporary  screens  of  board 
or  dry  sail  cloth.  In  any  case  the  temperature  should  be  grad- 
ually, very  gradually  raised,  the  object  to  be  attained  being  that 
the  higher  temperature  of,  say,  a  very  few  degrees,  shall  pene- 
trate right  into  the  substance  of  the  meat,  before  the  outer  sur- 
face is  subject  to  a  further  increase  of  temperature.  If  this  is 
done  carefully,  the  meat  so  thawed,  providing  it  has  been  care- 
fully chilled  or  frozen,  will  turn  out  well  when  cooked.  If  this 
is  not  done,  the  flavor  of  the  meat  and  its  quality  will  be  very 
much  deteriorated. 

In  thawing  out  holds  it  is  best  to  circulate  hot  brine  in  the 
brine  coils,  rather  than  to  use  fires,  or  similar  arrangements.    The 


HANDLING  MEAT  AND  PRODUCE.  Ilg 

brine  should  be  gradually  increased  in  temperature,  and  should 
be  kept  in  circulation  until  the  hold  is  thoroughly  dried.  The 
insulation  will  be  all  the  better  for  it. 

HANDLING   MEAT  AND  PRODUCE   WHEN   LOADING  AND  DISCHARGING. 

Do  not  handle  the  produce  more  than  can  possibly  be  helped. 
On  no  account  place  the  hands  on  the  meat  or  fruit  that  is  to  be 
stored,  if  it  can  possibly  be  avoided.  The  enormous  quantity  of 
frozen  sheep  which  are  brought  to  England  from  New  Zealand 
are  all  inclosed,  each  sheep  in  its  own  linen  bag,  which  avoids 
the  necessity  of  hands  touching  the  carcasses,  though  the  results 
of  touching  a  hard  frozen  substance  are  not  so  serious  as  those 
of  touching  a  chilled  meat  surface,  or  the  surface  of  fruit,  etc. 
The  linen  bags  also  form  a  very  convenient  arrangement  for 
identifying  particular  consignments,  each  bag  being  marked  with 
the  owner's,  consignor's,  or  consignee's  name. 

With  chilled  beef  and  with  fruit  the  matter  is  sometimes  a  very 
difficult  one.  Fruit  should  be  handled  in  crates,  so  that  the  hands 
do  not  touch  the  produce  at  all,  either  loading  or  unloading.  In 
the  case  of  bananas,  they  can  be  handled,  or  should  be,  by  the 
stalks. 

One  great  source  of  trouble  in  connection  with  chilled  meat  is 
the  muggy  atmosphere  that  is  so  common  in  the  United  King- 
dom, and  is  also  met  with  in  every  part  of  the  world  where  fogs 
prevail  at  certain  times  of  the  year.  This  muggy  atmosphere 
contains  moisture  held  in  suspension  in  the  well  known  manner. 
It  is  able  to  hold  a  certain  quantity  of  moisture  when  at  a  cer- 
tain temperature.  If  any  portion  of  the  air  is  cooled,  a  deposit 
of  a  certain  portion  of  the  moisture  it  contained  follows,  usually 
on  the  cold  surface,  bringing  the  cooling  effect.  When  chilled 
meat  is  removed  from  the  hold  to  the  railway  trucks,  say,  or  to 
a  cold  store,  where  there  is  one  on  the  dock  side,  there  is  always 
a  great  danger  if  the  atmosphere  is  in  that  muggy  condition 
mentioned,  of  the  deposit  of  moisture  upon  the  surface  of  the 


Il6  COLD    STORAGE    ON    BOARD    SHIP. 

meat,  which  is  nearly  always  at  a  considerably  lower  temperature 
than  that  of  the  atmosphere,  with  the  result  that  the  meat  is 
seriously  deteriorated,  and  its  market  value  reduced.  The  prob- 
lem of  how  to  meet  this  is  an  exceedingly  difficult  one. 

Probably  the  best  method  is,  to  ascertain  by  means  of  a  hy- 
grometer the  actual  humidity  of  the  atmosphere,  to  note  carefully 
its  temperature,  and  if  possible  to  raise  the  temperature  of  the 
meat  to  be  discharged  to  that  of  the  atmosphere,  or  a  little  above 
it.  Whether  moisture  deposits  from  the  atmosphere  on  the  meat 
will  depend  upon  the  temperatures  of  the  two,  and  upon  the 
vapor  tensions  of  the  moisture  in  the  atmosphere,  and  that  issu- 
ing from  the  meat.  It  will  be  better,  if  possible,  for  a  little 
vapor  to  be  given  off  from  the  meat,  than  for  moisture  to  be  de- 
posited upon  it.  If  the  meat  is  carried  into  cold  store  almost 
directly  from  the  ship,  or  at  any  rate  very  shortly  after,  it  will 
be  quite  easy  to  reduce  the  temperature  again,  and  to  do  it  care- 
fully, and  the  meat  will  be  preserved. 

It  is  not  so  easy  to  arrange  this  where  the  meat  is  to  be  dis- 
charged into  refrigerating  railway  cars,  and  it  is  absolutely  im- 
possible where  the  meat  is  to  be  discharged  into  ordinary  railway 
cars  or  carts.  In  the  latter  cases  all  that  can  be  done  is  to  wrap 
each  individual  carcass  with  dry  substances  that  are  good  thermal 
insulators,  so  that  the  hands  of  the  carriers  may  not  touch  them, 
and  that  the  moisture  may  not  be  deposited  directly  on  them. 
Almost  any  form  of  cloth,  providing  that  it  is  thoroughly  dry, 
will  answer,  and  a  very  good  thing  for  temporary  use,  if  it  can 
be  obtained,  failing  anything  else,  is  brown  paper.  It  must  not 
be  forgotten,  of  course,  that  all  fabrics  and  paper  are  porous,  and 
absorb  moisture,  and  therefore  they  should  be  removed  immedi- 
ately their  work  is  done,  if  they  have  become  wet.  The  wrap- 
pings also  should  be  as  thick  as  possible,  so  as  to  offer  the  high- 
est resistance  to  the  passage  of  heat  from  the  atmosphere  to  the 
meat,  and  also  to  absorb  as  much  of  the  moisture  that  may  be 
deposited,  as  possible. 


FAULTS  IN    AN   ABSORPTION   PLANT.  117 

In  the  railway  trucks,  even  if  they  are  not  fitted  with  cooling 
apparatus,  providing  that  they  are  open,  constructed  in  the  same 
manner  as  crates  are,  and  providing  that  they  are  placed  in  the 
cars  in  such  a  manner  that  the  air  can  get  all  around  them,  if 
the  trains  are  hauled  away  quickly  as  they  are  loaded,  it  is 
probable  that  not  much  harm  will  take  place  if  the  above  pre- 
cautions are  taken. 


FAULTS  IN  AN   ABSORPTION   PLANT. 

A  large  portion  of  the  instructions  given  in  connection  with 
faults  in  a  compression  plant  apply  also  to  an  absorption  plant, 
because,  as  explained  in  the  earlier  part  of  the  articles,  the 
condenser,  evaporator,  brine  circulation  and  air  circulation  are 
common  to  both  compression  and  absorption  plants,  but  the 
absorption  plant  has  faults  peculiar  to  itself.  In  it  the  generator 
with  its  accessories,  the  analyser  and  rectifier,  represents  the 
compression  side  of  the  compressor,  and  the  absorber  represents 
the  suction  side.  It  will  be  remembered  that  the  ammonia  is 
driven  off  from  the  aqueous  solution  in  which  it  is  carried  in 
the  generator,  by  the  aid  of  heat,  that  it  then  passes  through 
the  analyser  and  the  rectifier  to  the  condenser,  where  it  be- 
comes liquid,  and  from  the  condenser  takes  the  same  path  as 
with  a  compression  plant,  through  the  expansion  valve  and  the 
expansion  coils,  coming  back  to  the  absorber  instead  of  to  the 
compressor.  The  high-pressure  side  of  the  plant  therefore  will 
consist  of  the  generator,  the  analyser,  the  rectifier,  and  the  con- 
denser, while  the  low-pressure  side  will  consist  of  the  expansion 
coils  and  the  absorber.  Pressure  gages  are  fixed  at  any  con- 
venient spot  on  the  high-pressure  side.  In  the  form  that  is  most 
in  use  in  the  United  Kingdom,  that  made  by  Messrs.  Ransomes  & 
Rapier,  the  gage  is  placed  on  the  rectifier,  the  gage  registering 
low  pressure  being  placed  on  the  absorber. 

Practically  the  same  rules  hold  good  as  with  the  compression 


Il8  COLD   STORAGE  ON   BOARD  SHIP. 

i 

plant,  viz.,  'watch  the  gages,"  but  in  addition  to  the  pressure 
gages  mentioned,  there  are  also,  in  the  absorption  plant,  two 
very  useful  glass  liquid  gages,  one  on  the  generator  and  one 
on  the  absorber,  showing  the  height  of  the  liquid  in  these  vessels. 
Messrs.  Ransomes  also  fix  a  liquid  gage  on  the  condenser,  but 
there  is  no  reason  that  a  liquid  gage  should  not  be  fixed  upon 
all  condensers.  Where  there  is  a  receiver  between  the  con- 
denser and  the  expansion  valve,  it  is  always  usual  to  have  a 
liquid  gage,  showing  the  height  of  the  liquid  in  the  receiver.  It 
will  be  remembered  also  that  the  continuous  working  of  the 
apparatus  is  maintained  by  the  continual  exchange  of  weak  and 
strong  liquid,  between  the  generator  and  the  absorber.  Weak 
liquid,  as  already  explained,  has  a  higher  specific  gravity  than 
strong  liquid,  and  as  the  gas  is  driven  off  from  the  solution  in 
the  generator,  the  weak  liquid  sinks  to  the  bottom.  In  Messrs. 
Ransomes'  plant  the  weak  liquid  is  forced  by  the  pressure  of 
the  gas  in  the  generator  towards  the  absorber,  passing  through 
the  apparatus  called  the  exchanger,  on  its  way.  In  the  absorber, 
on  the  other  hand,  the  continual  passage  of  the  gas  from  the 
expansion  coils  into  the  liquid  present  in  the  absorber  vessel, 
constantly  increases  the  strength  of  the  liquid,  from  the  ammonia 
point  of  view,  and  the  strong  liquid  is  carried  back  to  the  gen- 
erator, passing  on  its  way  through  the  exchanger,  by  the  aid  of 
a  small  pump  provided  for  the  purpose. 

In  Messrs.  Ransomes'  apparatus  there  is  an  automatic  float 
valve,  consisting  of  a  vessel  ellipsoidal  in  shape,  in  which  there 
is  a  port  opening  to  a  pipe  leading  to  the  exchanger,  and  thence 
to  the  generator.  As  the  absorber  becomes  charged  with  weak 
liquid  from  the  generator  on  the  one  hand,  and  with  ammonia 
from  the  expansion  coils  on  the  other,  the  height  of  the  liquid 
gradually  increases,  its  strength  also  increasing,  and  at  a  certain 
height  it  overflows  into  the  vessel  containing  the  automatic  valve. 
In  this  vessel  is  a  float  controlling  the  valve  and  when  a  certain 
quantity  of  the  strong  liquid  has  passed  into  the  valve  vessel, 


FAULTS  IN   AN  ABSORPTION   PLANT.  1IQ 

the  float  rises,  opens  the  valve  leading  to  the  exchanger,  and 
allows  the  pump  to  deliver  the  strong  liquid  to  the  exchanger 
and  the  generator. 

There  is  the  same  difference  between  the  pressures  on  the 
high-pressure  and  low-pressure  side  of  the  expansion  valve  as 
in  the  compression  system,  the  pressures  ranging  as  in  that 
system,  on  the  condenser  side,  from  135  pounds  to  200  pounds 
per  square  inch,  while  the  pressure  on  the  evaporator  and 
absorber  side  is  usually  in  the  neighborhood  of  15  pounds  per 
square  inch.  Both  vary,  however,  as  in  the  compression  system, 
with  the  conditions  ruling.  On  the  condenser  side  the  pressure 
increases  with  the  temperature  of  the  circulating  water  of  the 
condenser.  Messrs.  Ransomes  give  a  list  in  their  instructions, 
stating  that  with  cooling  water  at  50  degrees  F.  inlet,  and  95  de- 
grees F.  outlet,  the  condenser  pressure  will  be  135  pounds ;  with 
water  at  60  degrees  F.  inlet  the  pressure  rises  to  150  pounds,  and 
so  on  up  to  water  at  90  degrees  F.  inlet,  115  degrees  F.  outlet, 
when  the  condenser  pressure  is  200  pounds. 

In  addition  to  this,  the  pressure  of  the  steam  employed  in 
driving  the  ammonia  out  of  the  cylinder  in  the  generator  varies 
with  the  temperature  of  the  condensing  water.  In  other  words, 
the  temperature  and  the  quantity  of  heat  it  is  necessary  to  deliver 
to  the  ammonia  solution  in  the  generator  increases  as  the  temper- 
ature of  the  condenser  cooling  water  increases.  Messrs.  Ran- 
somes give  the  following  figures:  With  cooling  water  at  50  de- 
grees F.  inlet,  and  condenser  pressure  of  135  pounds  per  square 
inch,  steam  at  40  pounds  gage  pressure  is  required,  the  tempera- 
ture of  the  steam  being  about  287  degrees  F.  With  cooling  water 
at  60  degrees  F.  inlet,  and  the  condenser  pressure  at  150  pounds, 
the  steam  required  is  at  45  pounds  gage  pressure,  its  temperature 
being  about  292  degrees  F.  With  water  at  90  degrees  F.  inlet, 
and  condenser  pressure  at  200  pounds  per  square  inch,  steam  ai 
60  pounds  gage  pressure  is  required,  its  temperature  being  about 
307  degrees  F. 


120  COLD  STORAGE  ON  BOARD  SHIP. 

As  in  the  compression  system,  the  condenser  pressure  is  ruled 
by  the  temperature  of  the  condenser  cooling  water,  and  the 
pressure  of  the  steam,  or  the  temperature  of  the  steam  employed 
to  drive  off  the  ammonia,  depends  upon  the  condenser  pressure. 
As  with  the  compression  system,  anything  which  interferes  with 
the  cooling  of  the  condenser  increases  the  condenser  pressure, 
and  increases  the  pressure  of  steam  required,  while  on  the 
other  hand,  anything,  such  as  cooling  water  of  a  lower  temper- 
ature, which  enables  a  lower  condenser  pressure  to  be  carried, 
enables  also  a  lower  steam  pressure  to  be  employed,  and  prac- 
tically is  more  economical.  As  also  in  the  compression  system, 
the  pressure  in  the  absorber  depends  upon  the  temperature  to 
which  the  brine  or  the  air  to  be  cooled  is  reduced,  the  same 
rule  applying  as  with  the  compression  system.  As  in  the  com- 
pression system  also,  the  higher  the  pressure  in  the  absorber, 
the  less  work  the  steam  in  the  generator  has  to  do. 

The  points  to  be  looked  to  principally  in  the  absorption  system, 
apart  from  those  mentioned  in  previous  portions  of  the  article, 
as  to  the  deposit  upon  condenser  and  evaporator  pipes,  etc., 
are  that  proper  circulation  between  the  absorber  and  the  gen- 
erator shall  be  continually  carried  on.  If  the  ammonia  pump 
does  not  deliver  the  proper  quantity  of  strong  liquid  into  the 
generator  from  the  absorber,  the  quantity  of  ammonia  present, 
it  is  evident,  will  be  less  than  is  required  for  working  at  the 
given  steam  pressure,  and  consequently  the  condenser  pressure 
will  fall,  and  the  condensation  of  the  liquid  will  be  interfered 
with.  There  is  also  the  same  trouble  in  the  absorption  system 
from  shortage  of  ammonia.  In  the  absorption  system,  there  is 
not  only  the  possibility  of  ammonia  leaking  out  through  defective 
joints,  as  in  the  compression  system,  but  there  is  also  the 
possibility  of  its  leaking  into  either  of  the  vessels  through  which 
it  passes.  In  any  case,  whatever  the  cause  of  leakage,  shortage 
of  ammonia  leads  to  the  same  results  as  with  the  compression 
system,  to  inefficiency  of  the  plant  as  a  whole. 


FAUUS  IN   AN  ABSORPTION  PLANT.  121 

imperfect  condensation  may  also  lead  to  the  passage  of  am- 
monia gas,  with  the  ammonia  liquid,  through  the  expansion 
valve,  and  the  same  results  as  explained  in  connection  with  the 
compression  system.  But  with  the  absorption  system,  properly 
gaged,  the  engineer  has  always  a  guide  in  front  of  him.  When 
the  liquid  in  the  condenser  is  not  above  a  height  which  prevents 
gas  from  passing  into  the  expansion  coils,  when  the  expansion 
valve  is  open,  then  the  expansion  valve  must  be  kept  partially 
closed.  Again,  the  glass  gages  on  the  generator  and  absorber 
will  show  him  the  condition  of  the  liquids  in  these  vessels.  To 
a  certain  extent,  they  show  the  quantity  of  liquid  in  each,  which 
is  of  great  importance,  and  the  gage  upon  the  condenser  will 
show  the  quantity  of  liquid  ammonia  being  formed. 

There  is  the  same  trouble  also  in  the  absorption  system  from 
air  getting  into  the  system,  and,  being  practically  incompressible, 
setting  up  pressures  opposing  the  actual  working  pressures.  In 
the  absorption  system  the  result  of  the  presence  of  air  in  the 
system,  or  of  any  other  insoluble  gas,  such  as  hydrogen  in  the 
case  of  the  decomposition  of  ammonia,  is  an  increase  in  the 
pressure  on  the  absorber  gage  on  the  low-pressure  side  of  the 
system.  As  in  the  compression  system,  therefore,  a  constant 
watch  upon  the  gages  will  give  early  warning  that  something 
is  wrong,  and  further  examination  will  show  what  it  is. 

If  there  is  air  in  the  system,  it  is  discovered,  and  expulsion  is 
obtained  by  the  same  means  as  in  the  compression  system.  There 
is  a  valve  specially  arranged,  on  the  absorber,  for  the  purpose 
of  getting  rid  of  the  air.  An  India  rubber  tube  is  attached  to 
this  valve,  its  other  end  being  immersed  in  a  vessel  containing 
water.  When  the  valve  is  open,  the  air  is  driven  out,  and  may 
be  seen  bubbling  up  through  the  water;  and  when  all  the  air 
that  can  be  got  out  at  the  moment  has  passed,  the  water  will 
commence  to  smell  strongly  of  ammonia,  and  the  valve  is  then 
closed.  It  is  necessary  in  some  cases  to  repeat  the  operation 
several  times  before  all  the   air   is   got   rid  of,   as   it   lurks   in 


122  COLD  STORAGE  ON  BOARD  SHIP. 

pockets  in  the  pipes,  etc.,  and  only  gradually  finds  its  way  to  the 
point  of  exit. 

It  will  be  noted  that  the  absorption  system  is  free  from  the 
troubles  mentioned  in  connection  with  the  compression  system, 
arising  from  the  presence  of  oil.  Except  from  gross  careless- 
ness, there  should  be  no  oil  in  the  system  at  all.  Hence  the 
troubles  that  were  mentioned,  of  oil  being  carried  over  as  vapor, 
and  being  decomposed  into  its  constituents,  and  deposited  upon 
the  inside  of  condenser  and  expansion  pipes,  are  absent.  On  the 
other  hand,  the  guide  offered  by  the  temperature  of  the  delivery 
pipe  of  the  compressor  is  also  absent,  but  the  glass  gages  men- 
tioned offer  a  very  much  better  and  more  certain  substitute. 

COLD    CHAMBERS    IN    COLD    STORAGE    TRAMP    STEAMERS. 

The  arrangement  of  cold  chambers,  or  cold  holds,  in  the 
steamer  that  is  constantly  taking  one  class  of  produce,  has 
already  been  fully  described,  but  the  case  of  the  tramp  steamer, 
making  more  or  less  of  a  specialty  of  carrying  produce  in  cold 
atmospheres,  presents  certain  difficulties.  Where  the  produce 
carried  is  always  the  same  (say  always  chilled  beef,  or  always 
bananas),  the  holds  can  be  fitted  either  with  brine  pipes,  or  with 
cold  air  circulation,  and  there  is  no  difficulty  about  the  matter. 
But  it  is  the  essence  of  the  tramp  steamer,  that  it  takes  any 
cargo  that  offers,  and  it  may  happen  that  on  one  voyage  it  has 
to  take  chilled  beef,  and  on  another  voyage  fruit,  dairy  products, 
or  other  produce  requiring  cold  air. 

To  meet  these  requirements,  a  somewhat  novel  arrangement 
has  been  worked  out  by  a  Liverpool  engineer.  He  provides  brine 
circulating  pipes  overhead,  and  at  the  sides  of  the  holds,  and 
it  is  arranged  that  each  of  the  pipes  can  be  individually  shut 
off.  In  addition,  the  pipes  on  the  sides  of  the  holds  are  provided 
with  wood  screens  made  of  matched  board,  having  hinged  flaps 
at   the   top  and   the  bottom,   and   also,   in   certain   cases,    having 


COLD  CHAMBERS   IN    TRAMP    STEAMERS.  123 

alternate  boards  hinged.  He  further  provides  hinged  port-holes 
in  the  fixed  boards  of  the  screen.  The  use  of  these  arrange- 
ments is  to  provide  a  cold  air  circulation,  or  a  complete  brine 
cooled  atmosphere,  with  the  same  plant,  without  any  appreciable 
alteration  to  the  holds,  and  without  the  necessity  of  the  air 
cooling  arrangement  that  is  commonly  employed. 

When  chilled  meat  is  being  carried,  or  frozen  meat,  the  whole 
of  the  brine  pipes,  overhead  and  at  the  sides,  are  put  into  opera- 
tion, and  the  hinged  boards  and  hinged  port-holes  are  all 
arranged  wide  open.  The  cooling  effect  is  produced  directly  by 
the  brine  pipes,  assisted  slightly  by  a  certain  amount  of  air 
circulation.  When  fruit  or  dairy  produce,  or  anything  that  re- 
quires only  cold  air  circulation,  is  carried,  the  overhead  brine 
pipes  are  not  put  into  operation,  the  side  brine  pipes  alone  being 
operated,  and  to  the  extent  that  may  be  necessary  to  produce  the 
required  temperature.  The  air  is  cooled  by  driving  it  through 
a  duct  arranged  for  the  purpose,  over  the  side  brine  pipes,  out 
into  the  hold,  and  back  by  another  duct,  the  air  being  kept  in 
motion  by  means  of  a  fan  placed  at  any  convenient  position  be- 
tween the  outgoing  and  return  ducts.  It  is  stated  that  this 
arrangement  has  given  great  satisfaction,  and  overcomes  the 
difficulties  mentioned  above. 


THE   HEATING  AND  VENTILATING  OF  SHIPS. 


Both  heating  and  ventilating  have  only  within  recent  years 
received  serious  consideration,  either  ashore  or  afloat.  On 
shore  heating  has  been  confined,  in  the  United  Kingdom, 
almost  universally  to  open  coal  fires,  and  ventilation  to  open- 
ing windows  and  doors.  In  America  and  Canada,  heating  on 
shore  has  been  more  seriously  studied  for  some  considerable 
time,  because  of  the  more  severe  conditions  of  climate  at 
certain  times  of  the  year.  With  the  comparatively  mild  win- 
ters of  the  United  Kingdom,  a  well-warmed  room  in  cold 
weather  has  been  sufficient  for  most  individuals.  In  parts  of 
America,  and  practically  the  whole  of  Canada,  the  severe 
winters  have  obliged  householders  to  provide  means  of  heat- 
ing, not  only  living  rooms,  but  passages,  halls,  etc.,  and  this 
has  led  gradually  to  the  development  of  the  improved  forms 
of  heating  and  ventilation  that  are  now  common  on  both  sides 
of  the  Atlantic. 

The  same  remarks  apply  practically  to  heating  and  venti- 
lating on  board  ship.  In  the  great  majority  of  cases  until  re- 
cently, and  in  a  very  large  number  of  ships,  particularly  in 
small  craft,  even  now,  just  as  in  large  numbers  of  private 
houses  on  shore  in  the  United  Kingdom,  heating  has  been  ac- 
complished either  by  the  familiar  stove,  standing  in  the  middle 
of  the  mess  room,  with  its  chimney  passing  up  through  the 
deck  above,  as  shown  in  Fig.  i,  a  cabin  on  an  Ohio  river  tow- 
boat,  or  in  certain  cases  through  the  side  of  the  ship.  In  the 
saloons  of  passenger  steamers,   and  the  mess   rooms  of  the 


THE   HEATING   AND  VENTILATING  OF   SHIPS. 


125 


executive  officers  in  the  better  class  of  tramp  steamers,  the 
iron  stove  has  been  displaced  by  the  fireplace,  built  into  a  fire- 
proof recess,  similar  to  those  employed  on  shore.  Ventilation 
on  board  ship  has  been  confined  to  opening  ports  and  hatch- 
ways when  the  weather  allowed,  assisted  by  an  occasional 
windsail,  and  by  ventilators  leading  from  the  different  messes, 
saloons,  etc.,  to  the  upper  deck. 


FIG.    1. CABIN    OF    AN    OHIO    RIVER    TOWBOAT,    SHOWING    THE    OLD    FORM 

OF   CLOSED    HEATING    STOVE   AND    PIPE. 


The  advance  of  modern  science,  and  particularly  the  advance 
of  medical  science,  has  shown  this  method  of  ventilation,  or  ab- 
sence of  ventilation,  to  present  very  grave  dangers  to  those  on 
board  who  have  to  remain  below;  in  emigrant  ships,  for  in- 
stance, in  which  large  bodies  of  men,  women  and  children, 
often  of  all  nationalities,  often  of  not  too  cleanly  habits,  often 
again  of  not  too  robust  health,  have  been  confined  between 
decks,  with  very  little  air  from  outside  penetrating  to  them 


126  THE    HEATING   AND  VENTILATING  OF    SHIPS. 

whenever  the  weather  was  sufficiently  bad  to  oblige  ports  to  be 
shut  and  hatchways  to  be  closed. 

Modern  medical  science  teaches  that  in  such  cases  diseases, 
sometimes  unknown  to  their  possessors,  are  rapidly  propa- 
gated. It  is  now  known  that  diseases  are  communicated  by 
minute  organisms  variously  known  as  bacilli  and  bacteria,  and 
these  breed  rapidly  under  the  conditions  named.  The  same 
kind  of  thing  rules  on  shore,  where  large  numbers  of  men  and 
women  are  confined  in  small  spaces,  badly  ventilated,  as  in 
some  of  the  workrooms,  etc.,  that  were  common  not  long  since 
in  the  east  end  of  London.  In  addition,  it  is  well  known  that 
consumptives  are  frequently  sent  to  sea  with  the  idea  that  the 
sea  air  will  arrest  the  progress  of  the  disease,  and  if  there  be 
any  of  these  among  the  passengers  confined  between  decks  in 
bad  weather,  the  results  can  only  be  the  making  of  additional 
consumptive  patients.  Air  is  to  bacilli,  and  to  the  various 
emanations  from  unhealthy  subjects,  what  water  is  to  dirt. 

Water,  we  know,  if  properly  applied,  dissolves  dirt  and  other 
noxious  substances,  and  if  allowed  to  do  so,  will  carry  them 
away.  One  reason  why  Englishmen  and  Americans  are  so 
generally  healthy  and  so  usually  vigorous  is  because  they 
are  fond  of  water.  Some  of  the  other  nations  of  the  conti- 
nent of  Europe,  as  we  know,  and  particularly  some  of  those 
from  whom  large  portions  of  the  emigrants  are  drawn,  are  not 
so  fond  of  water,  and  the  consequence  is  they  bring  to  the 
steerage  quarters  germs  that,  if  allowed  under  the  conditions 
named,  will  breed  disease,  even  where  it  is  not  already  present 
or  incipient. 

There  are  two  methods  of  ventilating  that  may  be  applied 
both  to  buildings  on  shore  and  to  ships  afloat.  One  corre- 
sponds to  the  weekly  thorough  cleaning  that  the  good  house- 
wife bestows  upon  every  room  in  the  house.  As  we  are  some- 
times painfully  aware,  every  object  in  the  room  is  displaced, 
and  every  corner  is  subject  to  the  vigorous  cleaning  process, 


THE    HEATING   AND  VENTILATING   OF    SHIPS.     '  127 

under  which  disease  germs  cannot  exist.  Similarly  to  rooms 
on  shore,  the  'tween  decks,  cabins,  etc.,  afloat  may  be  cleansed 
by  throwing  them  open  to  a  vigorous  current  of  air,  when  the 
weather  allows,  by  opening  all  hatchways,  all  ports,  and 
moving  everything  and  seeing  that  the  air  current  penetrates 
to  every  corner,  just  as  the  housewife's  broom  does  in  the 
cleansing  process. 

The  other  method,  which  is  more  rational,  and  which  modern 
science  has  approved,  is  to  direct  a  current  of  air  from  the 
place  where  it  is  to  be  obtained  in  its  purest  form  into  each 
living  room,  as  far  as  possible  into  each  corner  of  it,  and  to 
carry  it  away  in  a  direction  different  from  that  at  which  it 
entered,  carrying  with  it  the  disease  germs,  the  emanations 
referred  to,  and  the  carbonic  acid  that  has  been  formed  by  the 
breathing  of  the  occupants  of  the  quarters,  and  also  in  minute 
particles  of  dust  that  may  be  present.  Certain  conditions  are 
necessary  in  connection  with  the  ventilating  air  current,  just 
described.  It  must  be  a  very  gentle  current  that  cannot  be 
felt,  except  under  special  conditions,  such  as  when  passing 
through  the  tropics.  In  temperate  climates  what  is  known  as 
a  draft  must  be  avoided,  and  that  is  one  reason  why  the  ven- 
tilation of  houses  is  somewhat  difficult.  By  a  draft  is  under- 
stood a  current  of  air  passing  through  a  room  or  living  place, 
such  as  a  cabin  or  mess  room,  at  such  a  velocity  that  the  heat 
of  the  body  is  carried  off  more  rapidly  than  the  circulation  of 
the  blood,  and  the  chemical  action  of  the  food,  etc.,  supplies  it, 
with  the  result  that  persons  subjected  to  the  draft  catch  cold. 

The  rationale  of  the  process  is  as  follows :  Air,  when 
passing  over  any  object  at  a  higher  temperature  than  itself, 
abstracts  heat  from  it,  every  cubic  foot  of  air  passing  over 
(say)  a  human  body  abstracting  a  certain  quantity  of  heat,  in 
proportion  to  the  difference  of  temperature  between  the  air 
and  the  body,  and  in  proportion  to  the  velocity  at  which  the 
air  travels,  up  to  a  certain  limit.    In  addition,  as  we  know,  the 


128  THE   HEATING   AND  VENTILATING  OF   SHIPS. 

human  body  is  constantly  perspiring  and  there  is  always  a 
minute  film  of  moisture  present  on  the  skin.  The  quantity  of 
moisture  present,  due  to  this  cause,  varies  with  the  individual. 
Some  persons  perspire  very  freely,  others  hardly  at  all.  Again, 
everyone  perspires  more  when  the  weather  is  warm  than 
when  it  is  cold,  and  again  more  under  exertion  than  when  at 
rest.  In  any  case,  the  air  current,  passing  over  the  body, 
converts  the  moisture  present  on  the  skin,  and  which  pene- 
trates through  the  clothes,  etc.,  into  vapor,  and  in  doing  so, 
extracts  heat  from  the  body.  Water  and  other  liquids,  it  will 
be  remembered,  can  assume  the  form  of  vapor  only  by  absorb- 
ing into  themselves  a  certain  definite  quantity  of  heat.  When 
the  perspiration  upon  the  body  is  transformed  into  vapor, 
nearly  the  whole  of  the  heat  required  to  enable  it  to  become 
vapor  is  taken  from  the  body  itself.  This  is  the  reason  why 
perspiration  is  so  good  in  hot  climates,  and  why  doctors,  and 
those  who  are  accustomed  to  the  tropics,  are  so  insistent  upon 
the  production  of  perspiration.  In  the  tropics  one  frequently 
hears  "old  stagers"  say  they  feel  all  right  as  long  as  they  can 
perspire.  The  evaporation  of  the  vapor  cools  the  body,  and  a 
gentle  current  of  air,  passing  over  the  body,  accomplishes  this. 
In  temperate  climates,  however,  and  in  cold  climates,  where 
it  is  required  to  keep  the  heat  in  the  body,  a  draft  of  air  pass- 
ing over  it  tends  to  cool  unduly  the  particular  part  over  which 
it  passes,  and  to  produce  the  unpleasant  feelings  we  know  as 
catching  cold.  Consequently,  one  of  the  first  requirements 
is  that  the  velocity  of  the  air  in  temperate  climates  should  be 
such  as  not  to  be  felt.  In  the  institutions  on  shore,  for  in- 
stance, which  have  adopted  mechanical  systems  of  ventilation, 
it  is  impossible  to  tell,  without  making  special  tests  for  the 
purpose,  that  any  air  current  is  passing. 


SPECIAL  REQUIREMENTS  ON   BOARD   SHIP.  129 

SPECIAL    REQUIREMENTS    Oy    BOARD    SHI*\ 

The  requirements  of  ventilation  and  heating  on  board  ship 
are  different  in  a  great  many  cases  from  those  on  shore.  On 
shore,  even  in  countries  where  there  are  large  variations  of 
temperature,  as  in  the  United  States,  Canada,  Russia,  etc.,  dif- 
ferent temperatures  are  confined  to  certain  parts  of  the  year. 
Thus,  during  certain  months  of  the  winter,  a  very  low  tem- 
perature rules,  while  during  certain  other  months  of  the  sum- 
mer a  high  temperature  may  rule.  In  such  countries  as  the 
United  Kingdom,  the  variation  of  temperature  is  usually  verj 
gradual  indeed.  On  the  other  hand,  a  ship  trading  (say)  be 
tween  Liverpool  or  New  York  and  the  Cape  of  Good  Hope,  ol 
between  Liverpool  or  New  York  and  San  Francisco,  will  ex- 
perience wide  differences  of  temperature  in  very  short  periods 
of  time.  Thus,  supposing  the  ship  leaves  either  Liverpool 
New  York  or  Boston  in  the  depth  of  winter,  for  San  Fran- 
cisco, the  temperature  will  at  first  be  very  low;  it  will  grad- 
ually increase  until  in  the  tropics  it  will  be  very  high.  It  will 
again  decrease,  and  in  the  neighborhood  of  Cape  Horn  may  be 
very  low  again,  gradually  increasing  once  more  as  she  makes 
her  "northing,"  and  so  on. 

Further,  there  is  a  very  important  matter  that  has  to  be  con- 
sidered in  connection  with  the  ventilation  of  ships  which  pass 
through  the  tropics,  and  of  others  which  go  to  other  climates, 
viz.,  that  of  the  humidity  of  the  atmosphere.  Humidity,  as  we 
know,  varies  considerably,  and  the  variation  has  a  very  im- 
portant bearing  upon  the  effect  of  a  current  of  air  upon  the 
human  body.  It  was  mentioned  above  that  in  the  tropics,  for 
instance,  if  one  is  perspiring,  a  gentle  current  of  air  has  a 
cooling  effect,  by  evaporating  the  perspiration,  but  this  is  only 
on  condition  that  the  atmosphere  itself  is  not  already  saturated 
with  moisture,  as  it  is  at  certain  times  of  the  year,  and  as  it  may 
be  quite  easily  between  decks  at  almost  any  time.  The  capacity 
of  the  atmosphere  for  moisture  varies  with  its  temperature, 


130  THE   HEATING   AND  VENTILATING   OF    SHIPS. 

according  to  the  curve  shown  in  Fig.  2.  It  will  be  noticed  that 
the  capacity  for  moisture  goes  up  very  rapidly  after  a  tempera- 
ture of  400  F.  is  reached.  Thus,  at  400  F.  its  capacity  is  3 
grains  per  cubic  foot;  at  6o°  F.,  6  grains;  at  8o°  F.,  11  grains, 
and  at  ioo°  F.,  20  grains.  Dry  air,  therefore,  at  a  high  tem- 
perature has  a  larger  capacity  for  moisture  than  dry  air  at  a 
lower  temperature. 

But  the  ability  of  the  atmosphere  to  evaporate  moisture  from 
any  substance,  or  body  of  liquid,  depends  very  largely  upon 
its  own  condition  of  saturation.  Thus,  if  it  is  already  fully 
saturated  with  moisture,  no  evaporation  will  take  place  from 
the  body  over  which  it  passes,  and,  under  certain  conditions, 
deposit  of  moisture  may  even  take  place  from  the  atmosphere 
onto  the  body.  The  question  whether  moisture  shall  be  evap- 
orated from  any  body,  or  be  deposited  from  the  atmosphere  on 
the  body,  depends  upon  the  tension  of  the  vapor  issuing  from 
the  body,  as  opposed  to  the  tension  of  the  vapor  present  in  the 
atmosphere.  The  tension  of  the  vapor  in  the  atmosphere  de- 
pends upon  its  degree  of  saturation,  while  the  tension  of  the 
vapor  issuing  from  the  body  depends  upon  its  temperature. 

Hence,  when  the  atmosphere  is  in  the  condition  we  know  as 
"muggy,"  that  is  to  say,  when  it  is  saturated  with  moisture,  as 
it  is  in  the  tropics  just  before  the  rainy  season,  and  as  it  may 
easily  be  between  decks,  and  particularly  in  the  stoke  hold 
under  certain  conditions,  even  with,  a  ventilating  current  pass- 
ing, the  cooling  effect  that  should  be  obtained  is  not  present. 
On  the  other  hand,  with  a  warm,  dry  air,  used  as  a  ventilating 
current,  and  having  a  large  capacity  for  moisture,  as  explained 
above,  the  evaporation  from  the  body,  even  with  a  compara- 
tively gentle  air  current,  may  be  so  great  as  to  produce  a 
serious  cooling  effect,  though  the  air  itself  is  comparatively 
warm.  Hence,  where  a  ventilating  air  current  is  employed,  in 
temperate  or  cold  climates,  it  may  be  necessary  to  add  mois- 
ture to  the  air  current,  in  order  that  the  cooling  effect,  owing 


SPECIAL  REQUIREMENTS   ON    BOARD    SHIP. 


131 


to  the  possible  evaporation  from  the  body,  may  be  reduced. 
It  will  be  understood  that  while  in  a  hot  climate,  warm,  dried 
air  passing  over  warm  bodies  produces  a  delicious  cooling 
effect,  in  temperate  or  cold  climates,  during  the  cold  season, 
the  same  warm,  dry  air  may  produce  an  undue  cooling  effect, 


20 1 1 

L                          I 

r 

7- 

t 

4- 

t 

f 

12                                                                                                                           J- 

L 

J7 

10                                       5                                                            f- 

Z 

T                   Z 

/ 

n  —  ,.     _.,  .   .. , ■     .    _ 

10° 


30 =         40°         50°         60°         70 
Temperature  Fahrenheit 


80° 


100 


FIG.    2. CAPACITY    OF    AIR    FOR    VAPOR,    AT    VARIOUS    TEMPERATURES. 


a  cooling  effect  that  is  undesirable,  for  the  same  reason,  owing 
to  the  evaporation  of  the  perspiration.  Hence  it  is  necessary 
in  some  cases  to  add  moisture  to  the  air  current.  It  is  an 
axiom  among  heating  and  ventilating  engineers  that  a  moist 
air  current  of  comparatively  low  temperature  is  "warmer"  than 
a  dry  air  current  of  a  higher  temperature. 


132  THE   HEATING   AND  VENTILATING  OF    SHIPS. 

DIFFICULTIES    PECULIAR  TO   SHIP  WORK. 

One  of  the  difficulties  in  connection  with  both  heating  and 
ventilating  on  board  ship  is  the  fact  that  in  bad  weather  the 
ship  "knocks  about."  There  may  be  said  to  be  two  distinct 
problems  before  the  heating  and  ventilating  engineer  in  ship 
board  work,  viz.,  that  presented  by  the  ordinary  ship,  which 
behaves  like  a  cork  when  there  is  a  sea  on,  and  that  presented 
by  the  modern  ship,  which  keeps  a  practically  even  keel. 
Modern  naval  architects  who  have  designed  warships,  and 
those  who  have  designed  ocean  liners,  have  both  striven  after 
the  same  thing,  a  steady  platform  under  all  conditions,  but  for 
totally  different  reasons. 

A  steady  platform  is  required  by  the  modern  warship  in 
order  that  the  guns  may  be  properly  fought.  In  the  battle  of 
the  Sea  of  Japan,  it  is  stated  that  the  Russian  gunners  were 
very  much  handicapped  by  the  fact  that  their  ships,  being 
very  heavily  loaded  with  coal,  and  not  being  designed  to  keep 
an  even  keel,  rolled  very  much  in  the  heavy  sea  that  was  on, 
while  the  gunners  were  not  practiced  in  firing  with  the  ship 
rolling.  Even  the  most  practiced  gunlayer  cannot  do  so  well 
with  a  ship  rolling  as  with  a  ship  steady,  and  hence  every 
effort  has  been  made,  and  with  apparently  considerable  success, 
to  provide  a  steady  platform.  The  naval  architects  who  have 
designed  the  ocean  liners  have  striven  after  the  same  results, 
and  with  apparently  almost  equal  success,  in  order  to  neutralize 
the  effects  of  mal-de-mer.  With  the  increased  ocean  traffic, 
particularly  between  the  United  Kingdom  and  America,  the 
ship  which  can  carry  its  passengers,  even  through  a  gale  of 
wind,  with  little  danger  of  sea  sickness,  commands  the  largest 
share  of  the  traffic. 

Evidently,  ventilating  and  heating  problems  are  very  much 
simpler  in  these  ships  than  in  those  which  knock  about,  and 
the  more  a  ship  knocks  about,  the  more  difficult  are  the  two 
problems.    One  hears  tales  of  ocean  tramps,  generally  of  the 


DIFFICULTIES   PECULIAR  TO    SHIP   WORK.  133 

older  type,  rolling  so  badly,  if  there  has  been  any  sea  on,  that 
the  galley  fire  could  not  be  lighted,  say  between  Bilbao  and 
Cardiff,  and  so  on.  The  additional  difficulties  presented  by  a 
rolling  ship  in  the  problem  of  ventilation  and  heating  will  be 
dealt  with  later  on,  but  meanwhile  it  will  easily  be  understood 
by  anyone  who  has  sailed  in  a  ship  which  rolls  very  much  that 
everything  is  very  much  strained.  In  old  wooden  ships  it 
was  quite  common  to  see  the  ship's  side  bend  inwards,  as  that 
side  rolled  downwards,  the  resilience  of  the  timbers  assisting 
to  bring  her  up  again.  The  iron  shells  of  modern  ships  have 
not  the  resilience  of  the  old  wooden  ships,  but  they  must  give 
to  a  certain  extent,  and  every  roll  and  every  pitch  strains  every 
bolt,  duct,  etc.,  and  produces  eddies  in  water,  air,  and  so  on, 
that  are  used  for  heating  and  ventilating. 

Another  difference  that  arises  between  ventilating  on  shore 
and  ventilating  on  board  ship  is  the  air  current  created  by  the 
passage  of  the  ship  through  the  water.  On  shore  the  wind 
has  to  be  taken  into  account  in  designing  systems  of  ventila- 
tion for  buildings,  and  the  wind  must  also  be  taken  into 
account  in  connection  with  ship  ventilation,  and  in  some  cases 
with  heating,  but  the  passage  of  the  ship  through  the  water  is 
constant,  and  by  itself  it  creates  a  powerful  ventilating  cur- 
rent. For  instance,  the  maximum  velocity  of  air  in  the  ordi- 
nary ventilating  air  current  on  shore  is  5  feet  per  second,  and 
many  ventilating  engineers  prefer  even  the  lower  velocity  of 
3  feet.  The  tramp  steamer,  running  at  from  eight  to  ten  knots, 
produces  an  air  current  of  from  13  feet  to  17  feet  per  second ; 
at  16  knots,  which  is  a  very  common  speed  at  the  present 
day,  the  velocity  of  the  air  will  be  27  feet  per  second;  while 
that  of  the  Lusitania  is  somewhere  in  the  neighborhood  of  40 
feet  per  second. 

In  hot  climates,  the  air  current  produced  by  the  passage  of 
the  ship  will  be  very  useful  indeed  in  cooling  the  air  between 
decks,  etc.,  but  in  cold  climates,  and  in  particular  in  those 


134  THE    HEATING    AND   VENTILATING   OF    SHIPS. 

regions  in  which  whaling  ships,  sealers,  etc.,  have  to  cruise,  the 
air  current  is  a  very  serious  matter,  and  must  be  warmed,  as 
will  be  explained,  and  possibly  humidified,  before  being  allowed 
to  penetrate  between  decks. 

Ventilation  of  ships  has  one  important  advantage  over  ven- 
tilation on  shore  in  some  cases,  notably  in  some  of  the  large  and 
smoky  towns,  inasmuch  as  there  is  no  difficulty  whatever  in  ob- 
taining absolutely  pure  air,  rich  in  ozone,  the  most  powerful 
oxidizing  agent  available,  and  there  is  a  complete  absence  of 
any  necessity  for  cleansing  the  air.  On  shore,  in  large  towns, 
one  of  the  most  important  matters  in  connection  with  the 
ventilation  of  public  buildings  consists  in  the  purification  of  the 
air.  Various  devices  are  employed,  and  in  all  of  them  the 
quantity  of  dirt, — of  black  coaly  matter  such  as  steamers  too 
often  have  distributed  over  their  decks  when  burning  bad 
coal, — that  is  deposited  in  the  receptacle  provided  for  it,  is 
astonishing. 

METHODS    OF   HEATING    AVAILABLE. 

The  following  methods  of  heating,  which  are  in  use  on 
shore,  are  all  available  more  or  less  for  use  on  board  ship, 
some  of  them,  as  will  be  explained,  being  more  easily  adapted 
under  all  conditions,  and  some  of  them  again  not  being  suit- 
able for  ships  that  knock  about  in  a  sea  way,  put  being  quite 
practicable  for  those  which  keep  an  even  keel : 

1.  The  open  fireplace,  or  closed  stove  burning  coal. 

2.  Pipes  or  apparatus  in  which  hot  water  is  circulated. 

3.  Pipes  and  apparatus  into  which  steam  is  delivered. 

4.  Apparatus  in  which  electric  currents  are  employed. 

5.  Apparatus  in  which  the  air  is  warmed,  humidified,  and, 
if  necessary,  cooled. 

The  last  form  of  apparatus,  it  will  be  noted,  combines  heat- 
ing and  ventilating,  and  on  shore  that  is  the  latest  develop- 
ment.    Many  of  the  large  new  buildings,  such  as  hospitals. 


METHODS   OF   HEATING    AVAILABLE.  135 

government  and  municipal  buildings,  stock  exchanges,  etc., 
are  warmed  and  cooled,  where  necessary,  entirely  by  means  of 
the  air  current,  which  is  taken  hold  of,  cleaned,  dried  where 
necessary,  warmed  where  necessary,  moistened  where  neces- 
sary, and  so  on.  The  latest  development  of  heating  and 
ventilating  on  board  ship,  on  the  great  ocean  liners  and  in 
men-of-war,  is  on  these  lines. 

The  oYd  fireplace  and  stove,  though  it  still  holds  a  large 
place  in  the  warming  of  rooms  on  shore,  has  long  been  con- 
demned as  inefficient,  because  the  larger  portion  of  the  heat 
iberated  by  the  combustion  of  the  coal  passes  up  the  chim- 
ney. It  is  not  necessary  to  remind  marine  engineers  that  a 
coal  fire  will  burn  only  with  a  draft,  and  that  the  products 
of  combustion  are  carried  up  the  chimney,  necessary  with  all 
coal  fires,  and  with  it  the  larger  portion  of  the  heat  liberated. 
A  certain  quantity  of  heat  passes  out  into  the  room  from  the 
glowing  fire,  by  radiation,  but  it  does  not  heat  the  air  of  the 
room,  because  the  air  is  almost  transparent  to  heat  rays.  The 
rays  of  the  sun  pass  through  our  atmosphere  without  heating 
it  to  anything  like  the  extent  to  which  they  heat  any  object 
against  which  they  impinge,  and  the  same  thing  holds  with 
heat  rays  from  a  fire.  Rooms,  cabins,  saloons,  etc.,  however, 
in  which  either  open  fire  places  or  closed  stoves  are  used,  are 
appreciably  heated  after  the  fire  has  been  burning  for  some 
time,  unless  they  are  subjected  to  cold  air  drafts,  or  unless  the 
walls  of  the  cabin,  etc.,  are  also  the  unprotected  sides  of  the 
ship,  and  the  heat  is  thus  conducted  away;  because  the  heat 
rays  emanating  from  the  glowing  fuel  and  striking  upon  the 
furniture  of  the  room,  the  bulkheads,  etc.,  heat  them  up,  and 
they  in  turn  heat  the  air  with  which  they  are  in  contact,  con- 
vection currents  being  set  up  in  the  well-known  manner,  and 
The  whole  room  being  thoroughly  warmed. 

Where  closed  stoves  are  employed,  and  particularly  where 
a  certain  length  of  iron  chimney  connected  with  the  stove  is 


136  THE   HEATING  AND  VENTILATING  OF   SHIPS. 

^within  the  room  to  be  warmed,  the  heating  effect  produced  is 
considerably  greater  than  with  an  open  fireplace,  because  of 
the  radiation  from  the  stove  itself,  and  from  the  pipe. 

A  somewhat  interesting  method  of  heating  a  cabin,  which 
the  writer  remembers  to  have  seen  in  his  younger  days,  may 
be  worth  mentioning.  In  an  old  wooden  frigate  of  the  British 
Navy,  in  which  he  served,  the  commander  had  his  cabin  heated 
in  cold  climates,  as  when  going  around  Cape  Horn,  by  an  8- 
inch  spherical  shot,  heated  to  redness  and  suspended  from  the 
deck  above  by  an  iron  rod  screwed  into  the  plug  hole  of  the 
shot.  The  ship  was  armed  partly  with  old  8-inch  smooth  bore 
guns  firing  spherical  shot,  and  as  these  always  had  a  plug,  it 
was  an  easy  matter  for  the  armorer  to  screw  into  it  an  iron 
rod  having  a  hook  at  the  other  end,  for  suspending  from  over- 
head. The  result  was  very  good.  The  commander's  cabin 
was  a  fairly  large  one,  and  it  was  well  warmed,  but  the  pro- 
cess of  heating  was  rather  troublesome.  The  shot  had  to  be 
heated  in  the  galley  fire. 

For  many  ships,  tramps  for  instance,  sailing  ships,  and  the 
numerous  coasting  vessels,  barges,  and  so  on,  the  coal  stove 
with  its  chimney  passing  up  through  the  deck  will  probably 
long  remain  the  only  method  of  heating,  though  some  of  the 
apparatus  to  be  described  later  would  be  found  very  suitable 
for  tramps,  whalers,  sealers,  etc.,  and  even  for  the  five-masted 
sailing  ships  that  are  still  in  being. 

THE    SYSTEM     OF    HEATING    BY     HOT    WATER. 

This  is  the  favorite  system  on  shore,  but  so  far  it  has  not 
found  much  favor  on  board  ship,  because  of  the  difficulty 
mentioned  above,  introduced  by  the  motion  of  the  ship,  strain- 
ing different  parts  of  the  apparatus,  and  causing  currents  in 
the  water  with  increased  chances  of  air  lock.  Heating  by  hot 
water  is  a  very  simple  matter.  In  its  simplest  form  there  is  a 
boiler  specially  designed  for  heating  water  to  a  temperature 


HEATING  BY   HOT  WATER. 


137 


Splash  Plate 


Supply  Tank 

■f~\        Balance  Tank 


U 


Shade 

~~~ 


Deck 


— —  _'..;.'-,7 


2 


Main 


Deck 


_ 


: ; .," — — — :  - — 


":. 


Cabin 


Deck 


—>> 


'  _ 


—'      ~  ~ZZ       ,,     ,    . 


Aft 


Stoke  Hold 


Heater 


Forward 


FIG.  3.— HOT-WATER  HEATING  SYSTEM  APPLIED  TO  A  YACHT. 
RADIATORS  CONNECTED  BETWEEN  MAIN  RISER  AND  RETURN;  ALSO 
BETWEEN     PIPE    FROM     BALANCE    TANK    AND    THE    RETURN. 


138  THE   HEATING   AND  VENTILATING  OF   SHIPS. 

of  about  180  degrees  F.,  and  a  system  o*  pipes  connected  to 
the  bciler  in  such  a  manner  that  the  water  is  kept  continually 
circulating  from  the  hotter  portion  of  the  boiler  through  the 
pipes,  and  the  radiators,  as  they  are  called,  back  to  the  boiler. 
An  addition,  however,  is  usually  made  to  the  system  in  the 
shape  of  a  storage  tank.  Fig.  3  gives  a  diagram  of  the  usual 
arrangement  of  hot-water  heating  systems,  as  applied  on 
shore,  and  as  it  has  been  applied  in  certain  cases  on  board 
ship.  The  diagram  shown  is  taken  from  a  hot-water  system 
fitted  on  board  a  steam  yacht. 

The  special  boiler  employed  for  heating  the  water  may  be 
displaced  by  steam  from  the  boiler  supplying  the  ship's  en- 
gines, or  from  a  special  boiler  arranged  for  the  purpose,  or 
the  exhaust  steam  from  the  auxiliary  engines  may  be  used. 
Both  of  these  plans  are  adopted  on  shore,  the  heat  from  the 
steam  being  delivered  to  the  hot-water  service  by  an  appa- 
ratus which  goes  by  the  barbarous  name  of  "calorifier,"  one 
form  of  which  is  shown  in  Fig.  4.  This  will  be  recognized  by 
marine  engineers  as  a  feed-water  heater.  There  is  the  usual 
cylinder,  which  may  be  fixed  vertically  or  horizontally,  with 
pipes  inside  in  which  the  water  to  be  heated  circulates,  steam 
passing  all  around  them  in  the  remaining  space  inside  the 
cylinder.  Or  the  reverse  arrangement  may  rule :  the  steam 
may  pa*s  through  pipes  inside  the  cylinder,  and  the  water 
occupy  the  space  surrounding. 

The  calorifier  has  been  arranged,  in  certain  cases,  with  au- 
tomatic steam  control.  Fig.  4  shows  Royle's  automatic  steam 
control.  A  rod  of  steel  is  stretched  between  the  top  plate  of 
the  apparatus  and  the  casting  forming  the  bedplate,  and  is 
provided  with  a  pair  of  nuts,  enabling  it  to  be  tightened  or 
loosened.  A  valve  controlling  the  steam  supply  is  fixed  about 
the  middle  of  the  rod,  as  shown,  the  opening  of  the  valve 
being  controlled  by  a  spring  on  the  one  hand,  and  the  rod  on 
the  other.     The  expansion  and  contraction  of  the  body  of  the 


HEATING  BY    HOT   WATER.  139 

apparatus,  with  the  heat  delivered  to  it,  opens  or  closes  the 
steam  valve,  by  pushing  against  the  head  of  the  valve,  or  re- 
leasing it,  thus  increasing  or  decreasing  the  supply  of  steam, 
Another  form  of  control  consists  of  a  bent  tube,  inclosed  in 


FIG.      4. — ROYLE     CALORIFIER     WITH    AUTOMATIC    CONTROL. 

a   box,   operating  the   steam  valve   in   very  much   the   same 
manner. 

On  shore,  hot-water  heating  appliances  are  often  combined 
with  hot-water  supply.  This  arrangement  is  very  common  in 
private  houses,  and  also  in  hospitals,  infirmaries,  etc.     When 


140  THE    HEATING   AND  VENTILATING  OF   SHIPS. 

this  arrangement  rules  in  large  establishments,  it  is  usual  to 
have  a  hot-water  storage  tank,  in  addition  to  the  calorifier. 
The  arrangement  is  as  follows:  Steam  from  the  boiler  sup- 
plies heat  to  the  calorifier,  the  condensed  steam  being  carried 
back  to  the  hot  well.  The  water  pipes  from  the  calorifier  are 
connected  to  the  storage  tank,  and  the  water  is  kept  con- 
tinually circulating  through  the  storage  tank,  and  through  the 
calorifier.  The  supply  of  hot  water  for  the  establishment  is 
taken  from  the  storage  tank.  When  very  little  water  is  used, 
the  temperature  of  the  water  in  the  storage  tank  increases,  and 
the  controlling  apparatus  of  the  calorifier  reduces  the  supply 
of  steam,  or  completely  shuts  it  off,  until  water  is  used  again. 
When  water  is  used,  cold  water,  as  will  be  explained,  taking 
its  place  and  the  temperature  in  the  storage  tank  being  re- 
duced, the  temperature  of  the  calorifier  is  also  reduced  and 
the  steam  is  readmitted  and  so  on. 

High  and  Low-Pressure  Hot-Water  Heating. — There  are 
two  methods  of  heating  by  hot  water,  known,  respectively,  as 
high  and  low  pressure.  The  main  difference  between  the  two 
is  in  the  temperature  to  which  the  water  is  raised,  and  the 
velocity  at  which  it  circulates.  In  the  high-pressure  hot- 
water  system,  small  pipes,  usually  of  ^-inch  bore,  carry  a 
small  quantity  of  water  at  a  high  temperature  and  a  high  ve- 
locity, while  in  the  low-pressure  system  larger  pipes,  from  I 
to  6  inches  bore,  carry  a  larger  quantity  of  water  at  a  lower 
temperature  and  at  a  lower  velocity.  There  is  a  further  dif- 
ference between  the  two  systems  also,  in  that  the  high-pressure 
system  is  hermetically  sealed,  an  air  vessel  being  provided  to 
take  up  the  expansion  of  the  water  mentioned  below.  In 
the  low-pressure  system  a  balance  tank  is  usually  provided,  as 
shown  in  Fig.  3,  which  performs  the  double  office  of  taking 
up  the  expansion  of  the  water  and  supplying  any  waste  that 
may  take  place. 


DIFFICULTIES   IN    HEATING  BY   WATER.  141 

DIFFICULTIES  IN  CONNECTION  WITH   HEATING  BY  WATER. 

There  are  two  principal  difficulties  to  be  encountered  in 
heating  by  hot  water — the  expansion  of  the  water  itself  and 
the  presence  of  air  in  the  system.  Water  expands  approxi- 
mately 1/23  of  its  bulk  between  its  point  of  greatest  density 
(39  degrees  F.)  and  its  boiling  point  at  standard  barometric 
pressures.     The  following  are  the  actual  figures: 

Temperature  of  the  Water.  Relative  Volume. 

1. 

1.0075 
1.038 
1.043 
1.086 
1.148 
1.223 
1.310 

The  expansion  of  the  water  must  be  provided  for,  and  in 
the  high-pressure  system  this  is  done  by  the  expansion  pipe, 
mentioned  above,  fixed  at  the  highest  point  of  the  system  and 
connected  to  it.  The  arrangement  is  merely  a  pipe  calculated 
to  accommodate  a  certain  quantity  of  air,  in  proportion  to  the 
quantity  of  water  in  the  system,  and  to  the  temperature  of 
the  water.  The  proportions  recommended  by  Walter  Jones,  a 
past  president  of  the  Institution  of  Heating  and  Ventilating 
Engineers  of  Great  Britain,  are  as  follows: 

With  water  at  a  temperature  of  212  degrees  F.,  the  expan- 
sion pipe  should  have  an  air  space  equal  to  1/20  of  the  water 
space  in  the  whole  apparatus.  At  300  degrees  F.,  the  air  space 
should  be  one-eighth  of  the  water  space ;  at  400  degrees,  one- 
fifth  ;  at  500  degrees,  one-third,  and  at  600  degrees,  one-naif. 

The  operation  of  the  expansion  pipe  is  really  that  of  a 
buffer.  As  the  water  expands  it  is  forced  upwards,  and  the 
air  in  the.  expansion  pipe  is   compressed.     If  the  expansion 


39° 

F. 

100° 

F. 

200° 

F. 

212° 

F. 

3000 

F. 

4000 

F. 

5000 

F. 

6oo° 

F. 

142  THE   HEATING   AND  VENTILATING   OF    SHIPS. 

pipe  and  the  whole  of  the  system  is  sufficiently  strong  to 
withstand  the  pressure,  and  if  the  quantity  of  air  in  the  ex- 
pansion pipe  is  sufficient,  when  the  water  cools,  the  air  ex- 
pands, and  equilibrium  is  maintained  in  the  system  and  it 
works  safely.  The  great  danger  of  the  high-pressure  system 
is  the  possibility  of  explosion,  owing  to  the  very  high  pressures 
that  are  sometimes  present.  The  expansion  pipe,  it  will  be 
seen,  acts  very  much  as  a  safety  valve,  in  addition  to  its 
operation  as  a  buffer. 

With  the  low-pressure  system  there  is  no  danger  of  ex- 
plosion, except  in  case  of  frost  in  any  part  of  the  system,  a 
matter  that  will  be  dealt  with  below ;  because,  as  seen  in  Fig. 
3,  the  expansion  of  the  water  is  fully  provided  for  by  the 
balance  tank.  The  increased  volume  of  the  water  produced  by 
the  increased  temperature  meiely  flows  into  the  balance  tank 
harmlessly,  and  when  the  system  cools,  the  balance  tank  re- 
supplies  the  water  required  to  fill  the  pipes.  The  balance  tank 
or  auxiliary  tank  is  usually  connected  to  the  water-supply 
service,  so  that  any  shortage  of  water  in  the  system  caused  by 
leakage  or  evaporation  is  made  up  automatically.  The  balance 
tank  should  be  fixed  above  the  highest  part  of  the  pipe  and 
radiator  system. 

THE  AIR  TROUBLE. 

The  air  trouble  is  often  a  very  serious  one  in  both  high  and 
low-pressure  hot-water  systems,  and  it  is  the  trouble  that  is 
likely  to  arise  in  connection  with  hot-water  systems  on  board 
ship,  and  that  is  one  reason,  the  writer  believes,  why  hot-water 
heating  has  not  been  adopted.  As  marine  engineers  know,  air 
is  always  present  in  water.  It  is  lighter  than  water,  and  always 
finds  its  way  to  the  highest  part  of  the  hot-water  system,  and 
if  allowed  to  do  so  will  come  away  harmlessly.  On  the  other 
hand,  if  there  are  bends,  particularly  in  the  forms  of  inverted 
U's,  dips,  etc.,  in  the  pipe  system,  air  is  sometimes  trapped,  and 


THE   ARRANGEMENT   OF    HOT-WATER    HEATING    SYSTEMS.      143 

becoming  compressed  by  the  expansion  and  flow  of  the  water, 
sometimes  operates  against  the  flow  to  such  an  extent  as  to 
even  stop  it  altogether. 

Engineers  are  all  familiar  with  the  troubles  that  arise  with 
air  when  water  is  being  pumped.  In  particular,  the  old  trouble 
of  the  air  lock  in  the  bend  of  a  siphon  is  well  known;  air,  if 
allowed  to  collect  in  the  bend,  becoming  gradually  compressed 
and  interrupting  the  flow  of  water.  Something  similar  to  this 
is  of  somewhat  too  frequent  occurrence  with  hot-water  systems, 
and  it  will  easily  be  understood  that  when  a  ship  is  knocking 
about,  and  when  currents  are  produced  in  the  water  circula- 
tion, quite  independent  of  its  circulation  proper,  and  when 
possibly  air  may  leak  into  the  system  through  joints  being 
strained,  air  locks  may  occur  in  certain  parts  of  the  system, 
with  the  result  that  the  circulation  of  the  water  is  interrupted, 
heating  at  the  radiators  ceases  and  dangerous  heating  may 
take  place  at  the  boiler  or  calorifier.  The  air  locks  are  easily 
guarded  against  by  the  provision  of  air  valves,  which  allow 
the  air  to  escape  under  the  conditions  that  have  been  named. 
It  is  usual  on  shore  to  place  either  small  air  pipes,  or  air 
valves,  at  the  top  of  the  system,  and  also  at  the  tops  of  all 
bends,  etc.,  and  at  each  radiator,  so  that  any  air  that  is  trapped 
may  come  away  harmlessly. 

THE  ARRANGEMENT   OF   HOT-WATER   HEATING  SYSTEMS. 

There  are,  broadly,  two  methods  of  arranging  hot-water 
heating  systems,  both  on  the  high-pressure  and  low-pressure 
working.  It  is  necessary,  as  will  easily  be  understood,  for  the 
water  that  is  delivering  heat  to  the  rooms  to  be  warmed,  in 
order  to  make  a  complete  circuit.  Setting  out  from  the  hottest 
part  of  the  boiler  or  calorifier  it  ascends  through  what  is 
usually  known  as  the  riser  or  flow  pipe,  to  the  highest  part  of 
the  system,  and  is  connected  to  the  balance  tank  above  that,  or 
to  the  expansion  pipe,  as  explained.    Another  pipe  rises  from 


144 


THE    HEATING   AND  VENTILATING  OF   SHIPS. 


the  coolest  part  of  the  boiler  or  calorifier  to  the  same  level  as 
the  riser,  or  a  little  below  it.  This  is  the  return  pipe,  and  in 
one  method  of  distribution  the  heating  appliances  are  connected 
between  these  two,  very  much  as  electric  lamps  are  connected 
between  the  two  supply  cables,  and  as  shown  in  Fig.  5. 

The  heated  water  passes  from  the  boiler  through  the  riser, 
through  the  different  heating  appliances,  and  returns  to  the 


FIG.     5. TWO-PIPE    SYSTEM,    LOW-PRESSURE    HOT    WATER. 


boiler  by  the  return  pipe,  becomes  again  heated  in  the  boiler  or 
calorifier,  and  repeats  its  journey.  Where  there  are  two  or 
three  floors  or  decks  to  be  heated  from  the  same  apparatus,  the 
different  heating  appliances  are  connected  to  the  riser  or  flow 
pipe  and  to  the  return  pipe  of  each  floor  or  deck.  One  heating 
appliance  may  be  connected  between  the  flow  and  return,  or 
two  or  more,  according  to  the  difference  in  temperature  be- 
tween the  two,  and  to  the  sizes  of  the  heating  appliances 
and  the  quantity  of  heat  required  for  them.     Where  a  single 


THE   ARRANGEMENT  OF    HOT-WATER    HEATING   SYSTEMS.      145 

heating  appliance  is  connected  between  the  flow  and  return  it 
would  correspond  with  the  usual  arrangement  of  incandescent 
electric  lamps  connected  in  parallel.  Where  two  or  more  heat- 
ing appliances  are  connected  between  the  flow  and  return,  in 
such  a  manner  that  the  water  flows  through  them  consecu- 
tively, the  arrangement  would  correspond  to  the  parallel  series 
arrangement  of  incandescent  electric  lamps. 

There  is  a  third  arrangement,  corresponding  roughly  to  the 
series  system  adopted  in  electricity,  as  with  a  number  of  arc 


ssi 


FIG.    6. CONNECTIONS    OF    RADIATOR    TO    A    HOT-WATER 

SYSTEM    WITH    TWO-PIPE    DISTRIBUTION. 


lamps  employed  in  street  lighting,  from  a  Brush  arc  machine. 
In  this  system  the  flow  pipe  is  taken  to  the  highest  part  of  the 
service,  say  to  the  highest  deck,  or  a  little  above,  if  possible,  in 
the  funnel  casing,  and  is  there  connected  to  the  balance  tank 
or  the  expansion  pipe  in  the  usual  way;  but  the  two  connec- 
tions to  the  heating  appliance  are  made  to  two  portions  of  the 
return  main  pipe,  as  shown,  the  heating  appliance  being 
bridged  across  that  portion  of  the  pipe.  This  corresponds  to 
the  method  known  in  electrical  work  as  shunting. 


146 


THE    HEATING    AND   VENTILATING   OF    SHIPS. 


Fig.  7  is  a  diagram  of  a  number  of  radiators  fed  on  the  one- 
pipe  system,  the  radiators  being  bridged  across  a  certain 
length  of  pipe,  but,  as  will  be  noticed,  two  radiators  are  fed 
from  one  bridge,  and  in  this  case  the  connection  to  the  balance 
tank  is  separate.  Fig.  6  shows  the  connections  between  a 
single  radiator  and  the  two  pipes  on  this  system.  Fig.  8  is  a 
diagram  of  a  system  in  which  the  exhaust  from  a  gas  engine 
is  used  to  heat  the  water,  which  is  carried  to  a  tank  above  the 


FIG.    7. DISTRIBUTION    OF    LOW-PRESSURE    HOT    WATER    ON     THE 

ONE-PIPE   SYSTEM. 


highest  radiator,  connection  being  made  from  the  hot-water 
tank  to  the  balance  tank  above;  and  the  distributing  pipes 
commencing  from  the  hot-water  tank  and  returning  to  the 
water-jacket  of  the  engine,  and  thence  to  the  heating  appa- 
ratus, the  radiators  being  bridged  singly  across  short  lengths 
of  the  pipe.  Practically,  with  this  method,  the  heating  ap- 
pliance is  fed  by  a  shunt  current  from  the  return  supply  main 
of  the  service. 


THE   ARRANGEMENT   OF    HOT-WATER    HEATING    SYSTEMS.      147 

It  will  be  understood  that  what  is  required  for  the  supply 
of  any  heating  appliance  is  a  sufficient  difference  of  tempera- 
ture between  the  inlet  and  outlet  valves,  and  a  sufficient 
supply  of  water  to  keep  up  a  continual  flow  through  it,  and  of 
such  a  temperature  that  the  requisite  quantity  of  heat  will  be 
given  off  by  it.     In  practical  hot-water  heating,  the  difference 


FIG.     8. DIAGRAM     OF     A     HOT-WATER     SYSTEM     DRAWING     HEAT 

FROM     THE    EXHAUST    OF     A     GAS     ENGINE.         (BRITISH     INSTI- 
TUTION    OF     HEATING    AND    VENTILATING     ENGINEERS.) 

of  temperature  between  the  two  ends  of  any  radiator  is  usually 
not  more  than  10  degrees  F.,  and  it  is  evident  that  this  can 
be  obtained  either  by  having  a  very  small  difference  of  tem- 
perature between  the  main  flow  pipe  and  the  return  flow  pipe, 
but  with  comparatively  large  pipes,  bridging  the  heating  ap- 
pliance between  the  two  pipes,  as  explained;  or  by  having  a 
larger  difference  of  temperature  between  the  ends  of  the  flow 
pipe  and  return  pipe  at  the  source  of  heat,  with  smaller  pipes, 
and  a  smaller  quantity  of  water  flowing,  but  with  a  larger  dif- 
ference of  temperature  in  any  given  length  of  pipe. 


148  THE   HEATING   AND  VENTILATING   OF   SHIPS. 

To  take  an  instance,  supposing  that  ten  radiators  are  to  be 
supplied  from  a  given  source  of  heat,  and  that  each  radiator 
requires  a  difference  of  temperature  between  its  inlet  and  out- 
let valves  of  10  degrees,  as  explained,  and  a  flow  of  ten  gallons 
of  water  through  it  per  hour.  Evidently  this  can  be  supplied 
by  a  system  of  large  pipes,  giving  ioo  gallons  per  hour,  but 
with  a  difference  of  temperature  between  the  main  flow  and 
return  pipes  of  only  n  or  12  degrees  F.  at  the  source,  or  it 
can  be  supplied  by  pipes  carrying  only  10  gallons  per  hour, 
but  with  a  difference  of  temperature  between  the  main  flow 
and  return  pipes,  at  the  source  of  heat,  of  no  to  120  degrees 
F.  Practical  men  on  shore  incline  very  much  to  the  latter 
system,  because  it  enables  smaller  pipes  to  be  employed,  and 
they  caution  engineers  to  avoid  the  former  system,  because  the 
water  tends  to  become  "short  circuited";  that  is  to  say,  the 
nearer  radiators  receive  the  major  portion  of  the  heat.  Evi- 
dently the  matter  is  only  one  of  proper  arrangement. 

It  should  be  perfectly  practicable,  by  a  proper  system  of 
pipes,  to  arrange  that  the  difference  of  temperature  between 
the  main  flow  and  return  at  the  top  of  the  system  shall  be 
very  nearly  the  same  as  that  between  them  at  the  lower  por- 
tions of  the  system.  What  is  required,  of  course,  is  proper 
proportion  in  the  size  of  the  main  and  return  pipes,  and  proper 
proportion  in  the  pipes  connecting  them  to  the  radiators.  If 
the  main  flow  and  return  pipes  are  small,  and  if  again  the 
radiators  on  the  lower  decks  are  connected  to  them  by  com- 
paratively large  pipes,  they  will  undoubtedly  short  circuit  the 
system. 


FORMS    OF    HEATING    APPARATUS    WITH    HOT    WATER.         149 
FORMS   OF    HEATING   APPARATUS    WITH    HOT   WATER. 

Hot-water  apparatus  for  heating  rooms,  cabins,  alleyways, 
corridors  and  so  on  may  consist  simply  of  pipes  laid  around 
the  rooms,  the  saloons,  etc.,  and  through  the  corridors ;  or,  as 
is  more  frequently  arranged,  what  are  termed  "radiators" 
may  be  employed.  The  term  radiator  is  a  misnomer.  As  is 
explained  below,  the  heat  delivered  by  the  heating  appliance  is 
only  partly  by  radiation.  On  the  other  hand,  the  plain  pipes 
that  were  employed  in  the  early  days  of  steam  and  hot-water 
heating  are  quite  as  much  radiators  as  the  forms  of  apparatus 
usually  so  denominated.  Any  pipe  in  which  hot  water  or  steam 
is  passing  gives  off  heat  at  a  rate  directly  proportional  to  the 
difference  of  temperature  between  the  water  and  the  air  on 
the  outside,  and  again  in  direct  proportion  to  the  extent  of 
surface  exposed,  and  directly  to  the  conductivity  of  the  sub- 
stance of  which  the  pipe  is  composed,  and  inversely  in  pro- 
portion to  its  thickness. 

This  law  in  its  simple  form  is,  however,  applicable  only  to 
small  differences  of  temperature  and  small  values  of  tempera- 
ture of  the  surrounding  air.  The  heat  is  given  out  in  two 
ways,  by  radiation  and  by  convection.  Heat  passes  from  a 
heated  body  in  all  directions,  through  the  air  and  whatever 
substances  may  surround  >it,  by  what  is  called  radiation.  Ra- 
diant heat,  as  the  heat  delivered  by  radiation  is  termed,  has 
the  peculiar  property  that  it  passes  through  air  without  de- 
livering much  heat  to  the  molecules  of  the  air  itself.  Heating 
from  fires,  stoves,  etc.,  though  it  is  due  almost  entirely  to 
radiation,  arises  from  the  fact  that  the  radiant  heat  is  ab- 
sorbed by  the  articles  of  furniture  in  the  room,  by  the  walls, 
etc.,  and  is  afterwards  given  out  by  them,  partly  by  re-radia- 
tion, partly  by  convection,  and  partly  by  conduction.  In  addi- 
tion to  the  above,  any  heated  body  present  in  air,  as  in  any 
room,  cabin,  corridor,  saloon,  etc.,  gives  rise  to  convection  air 
currents.     The   air   in   the  neighborhood   of  the  heated  body 


150  THE   HEATING   AND  VENTILATING  OF    SHIPS. 

becomes  warmer  than  that  slightly  removed  from  the  body  and 
is  pushed  upwards  by  the  weight  of  the  colder  air,  a  fresh 
supply  of  air  taking  its  place,  becoming  heated  again,  and  so 
on,  the  result  being  that  a  continual  circulation  of  air  is  pro- 
duced, until  the  temperature  of  the  room  is  raised  to  that  of 
the  heated  body,  or  as  long  as  heat  is  delivered  to  the  body, 
and  is  carried  off  by  the  surrounding  air.  Every  heated  pipe 
and  radiator,  therefore,  gives  off  heat  both  by  radiation  and  by 
convection,  or,  as  it  is  sometimes  termed,  by  air  contact. 

Different  bodies  have  different  radiating  properties.  Cast 
iron,  for  instance,  radiates  0.65  B.  T.  U.  per  square  foot  per 
hour  for  each  degree  F.  difference  of  temperature  between  itself 
and  the  surrounding  atmosphere;  wrought  iron,  0.57  unit; 
rusted  cast  or  sheet  iron,  0.67  unit.  The  heat  distributed  by 
convection  is  independent  of  the  nature  of  the  heated  body, 
but  varies  with  the  form  of  the  body.  Cast  iron,  wrought 
iron,  wood,  etc.,  if  heated  to  the  same  temperature,  give  rise  to 
the  same  distribution  of  heat,  but  the  quantity  given  off  varies 
with  the  form.  The  quantity  of  heat  delivered  by  any  hot- 
water  pipe  or  radiator  depends  directly  upon  the  difference  of 
temperature  between  the  body  and  the  air,  upon  the  surface 
of  the  heated  body  exposed  to  the  air,  and  upon  its  form.  This 
again,  as  with  radiation,  is  true  only  for  low  figures.  When 
the  difference  of  temperature  between  the  heated  body  and  the 
surrounding  air  does  not  exceed  30  degrees  F.,  and  when  the 
temperature  of  the  air  surrounding  the  body  does  not  exceed 
60  degrees  F.,  the  above  laws  for  radiation  and  for  convec- 
tion or  air  contact  hold  good ;  but  when  the  difference  of  tem- 
perature exceeds  the  above  figure,  and  when  the  temperature 
of  the  air  surrounding  the  heated  body  exceeds  60  degrees  F., 
the  rate  at  which  heat  is  delivered  to  the  air  increases,  and  at 
a  very  much  more  rapid  rate  than  the  increase  of  the  dif- 
ference   of   temperature. 

The  French  savants  Dulong  and  Petit    experimented  upon 


FORMS    OF    HEATING    APPARATUS    WITH    HOT    WATER.         151 

the  subject  some  years  ago,  and  their  experimental  facts  have 
been  confirmed  by  another  French  savant,  Peclet,  whose  name 
will  be  remembered  in  connection  with  the  laws  of  transmis- 
sion of  heat  in  refrigerating  matters,  and  they  have  produced 
some  very  complicated  formulae,  which  need  not  be  given 
here,  but  from  the  results  of  which  Mr.  Thomas  Box,  whose 
standard  book  on  "Heating"  is  well  known,  has  worked  out  a 
table  of  what  he  terms  ratios,  representing  the  number  by 
which  the  result  of  the  simple  laws  referred  to  above  must  be 
multiplied,  to  give  the  correct  results.  The  multiplier  or 
ratio,  as  Box  calls  it,  ranges  from  unity  up  to  six.  That  is  to 
say,  the  results  obtained  by  applying  the  simple  laws  given 
above,  for  the  quantity  of  heat  delivered  by  a  hot  water  or 
steam  pipe,  with  a  certain  difference  of  temperature,  and  the 
other  conditions  as  mentioned,  have  to  be  multiplied  by  a 
factor  varying  from  a  trifle  over  one  up  to  six,  to  obtain  the 
actual  results.  It  will  perhaps  be  sufficient  if  a  few  figures 
are  given. 

For  a  difference  of  temperature  of  108  degrees,  which  is  ap- 
proximately that  which  would  rule  between  the  temperature 
of  water  in  a  hot-water  radiator  at  173  degrees  F.  and  the  sur- 
rounding air  under  conditions  showing  a  temperature  of  65 
degrees  F.,  the  multiplier  is  1.4.  For  a  difference  of  tempera- 
ture of  160  degrees  F.,  which  is  what  would  probably  rule 
with  steam  heating,  the  multiplier  is  in  the  neighborhood  of 
1.6.  Approximately,  therefore,  for  the  conditions  of  heating 
by  hot  water  or  steam,  the  laws  given  above  will  show  the 
quantity  of  heat  delivered  to  the  air,  when  a  multiplier  of  1.5 
is  brought  into  the  equation. 

Taking  ordinary  working  conditions,  the  formula  for  the 
quantity  of  heat  delivered  by  a  hot-water  radiator  would  be 
as  follows : 

0=^(7-70X14  +  ^  (T  -  7\)  X  1.4, 
where  Q  is  the  quantity  of  heat  in  B.  T,  U.  delivered  to  the 


152  THE   HEATING  AND  VENTILATING  OF   SHIPS. 

air  per  hour,  for  each  square  foot  of  surface  of  the  radiator 
exposed  to  the  air;  R  is  the  rate  at  which  heat  is  delivered 
by  radiation ;  A  that  by  convection,  and  T  and  Tx  are  the  tem- 
peratures of  the  radiator  and  the  surrounding  air. 

It  was  mentioned  above  that  the  form  of  the  heated  surface 
exercises  an  influence  upon  the  heat  delivered  to  the  air  by 
convection  currents,  or,  as  it  is  termed,  by  contact.  Thus  a 
sphere  delivers  very  much  more  heat  per  unit  of  surface,  and 
with  a  given  difference  of  temperature,  than  either  a  vertical  or 
a  horizontal  cylinder.  The  apparatus  most  employed  in 
heating,  by  hot  water  or  steam,  is  either  a  horizontal  cyl- 
inder in  the  form  of  pipes  fixed  as  explained,  or  vertical  pipes 
in  the  forms  that  have  been  given  to  radiators.  For  hori- 
zontal pipes,  the  quantity  of  heat  delivered  to  the  air  in  con- 
tact with  the  pipe,  for  every  degree  F.  difference  of  tempera- 
ture, and  for  every  square  foot  of  surface  of  pipe,  for  the 
pipes  usually  employed,  is  as  follows :  With  2-inch  pipe, 
0.728  unit;  3-inch,  0.626;  4-inch,  0.574;  6-inch,  0.523  unit. 
These  figures  are  the  values  of  A.  For  radiators  the  prob- 
lem is  rather  more  complicated,  in  the  matter  of  con- 
vection. 

The  French  savants  referred  to  have  threshed  the  matter 
out,  and  have  produced  some  formulae  applicable  to  all  cases, 
as  a  result  of  their  experiments,  and  the  formulae  are  appar- 
ently pretty  correct  in  practice.  They  are  very  complicated, 
however,  and  it  will  be  perhaps  sufficient  if  it  be  mentioned 
that  heat  liberated  by  convection  from  a  sphere  is  consider- 
ably more  for  any  given  surface,  and  in  a  given  time,  than 
from  a  cylinder;  and  again  the  heat  liberated  from  a  hori- 
zontal cylinder,  of  a  given  diameter,  is  usually  more  than 
from  a  vertical  cylinder  of  the  same  diameter.  The  rates 
for  horizontal  cylinders  given  above  were  taken  from  Mr. 
Box's  book. 

The  rate  with  vertical  pipes  does  not  appear  to  have  been 


FORMS    OF    HEATING    APPARATUS    WITH    HOT    WATER.         153 

measured,  but  Professor  Carpenter*  and  others  have  made 
some  very  interesting  experiments  upon  radiators  of  different 
forms,  heated  by  steam  and  hot  water.  The  radiators  experi- 
mented on  were  of  various  forms,  among  them  those  shown  in 
the  drawings;  also  some  consisting  merely  of  iron  pipes  of 
different  diameters  and  different  lengths,  arranged  some  hori- 
zontally and  some  vertically;  also  pipes  and  other  arrange- 
ments with  ribs  cast  on  them,  brass  tubes  plain  and  corru- 
gated, and  other  forms.  The  net  result  of  the  experiments 
conducted  by  Carpenter,  and  by  others  whose  work  he  quotes, 
appears  to  be  a  liberation  of  heat,  the  combined  effect  of  radi- 
ation and  convection,  ranging  from  1,25  B.  T.  U.  per  square 
foot  of  surface  per  1  degree  F.  difference  of  temperature  be- 
tween the  heated  surface  and  the  surrounding  air,  per  hour, 
up  to  2.89  B.  T.  U. 

The  best  results  are  obtained  with  pipes  or  radiators  of 
small  sectional  area,  the  highest  having  been  obtained  from  a 
plain  wrought-iron  pipe  1  inch  in  diameter,  100  feet  long,  in 
a  single  horizontal  line.  Increasing  the  size  of  the  pipes  or 
the  radiator  equivalent,  though  increasing  the  total  amount 
of  heat  liberated  from  a  given  length  of  radiator  or  pipe,  de- 
creases the  rate  per  square  foot  per  degree,  etc.  Fixing  ribs 
upon  the  outsides  of  pipes,  which  has  been  adopted  by  some 
manufacturers,  with  the  idea  that  the  increased  surface  gives 
increased  liberation  of  heat,  are  shown  by  the  experiments 
quoted  by  Professor  Carpenter  to  have  the  opposite  effect. 
Thus,  a  plain  cast-iron  pipe  without  ribs  liberated  2.54  B.  T.  U. 
per  degree  per  hour,  while  a  similar  pipe,  ribbed,  liberated  only 
1.72  Units.  Cast  iron  gives  better  results  than  wrought  iron,  on 
account  of  its  higher  radiation,  apparently,  and  brass  gives  a 
very  low  result.  As  mentioned  above,  the  rule  with  practical 
heating  and  ventilating  engineers  is  to  estimate  for  a  libera- 
tion of  1.6  to  2  units  per  degree  F.  per  square  foot  per  hour. 

•  Cornell   University,    Ithaca,   N.   Y. 


154  THE    HEATING   AND  VENTILATING   OF   SHIPS. 

In  the  writer's  view,  in  laying  out  heating  appliances,  it  will 
be  wise  to  estimate  for  the  liberation  of  heat  at  a  rate  not 
exceeding  1.5  B.  T.  U.  per  square  foot  of  surface  of  the  ra- 
diator exposed,  per  1  degree  F.  difference  of  temperature,  per 
hour. 

It  will  be  easily  understood  that  the  above  are  standard 
figures,  and  that  for  any  given  increase  of  temperature  de- 
sired, say  of  the  air  in  a  room,  all  that  is  necessary  is  to  con- 
vert the  rate  of  liberation  of  heat  given  into  increase  of 
temperature  of  air,  and  then  to  divide  by  the  number  of 
degrees  by  which  the  air  temperature  is  to  be  increased.  Thus, 
1  B.  T.  U.  will  raise  by  1  degree  F.  the  temperature  of  about 
55  cubic  feet  of  air,  if  in  the  neighborhood  of  60  degrees  F. ; 
or,  it  will  raise  the  temperature  of  11  cubic  feet  by  5  degrees 
F.,  and  so  on.  All  that  is  required  to  find  out  what  quantity 
of   heating    surface    is    necessary,    is    to    apply    the    following 

C  (T—  Ti) 

formula :    5"  =s where  S  is  the  radiat- 

55  X  i.5  X  (T,  —  7\) 

ing  surface  in  square  feet;  C  is  the  cubical  contents  of  the 
room  to  be  heated,  in  cubic  feet ;  7\  is  the  temperature  of  the 
air  when  heat  is  applied;  T  that  to  which  it  is  to  be  raised; 
T2  that  of  the  radiator. 

In  the  above  it  will  be  understood  that  the  question  of  venti- 
lation has  not  been  considered  at  all.  Heating  appliances  are 
considered  entirely  by  themselves,  and  on  the  supposition  that 
the  common  practice  is  followed,  of  placing  the  heating  ap- 
paratus in  any  convenient  position  in  the  cabin,  saloon,  etc., 
and  irrespective  of  any  mechanically-produced  air  current ;  and 
the  heating  effect  produced  by  the  apparatus  is  such  as  would 
follow  on  the  lines  of  what  would  be  called  natural  ventila- 
tion. The  temperature  of  the  room  in  which  the  appliance  is 
fixed  is  raised  to  a  certain  figure  by  the  operation  of  radiation 


FORMS    OF    HEATING    APPARATUS    WITH    HOT    WATER. 


155 


and  convection  currents  as  explained,  but  without  any  control 
having  been  exercised  over  the  air. 
Also,  in  the  above  formula  the  heating  up  of  air  only  is 


»G.     l>. DOUBLE-TUBE     AND     SINGLE-TUBE      RADIATORS     FOR     STEAM     OR      HOT 

WATER. 

considered  when  the  room  is  cold  and  heat  is  turned  low ;  but 
the  formula  also  applies  when  the  room  is  at  its  required  tem- 
perature, and  the  heating  appliance  has  to  make  good  the  heat 


156 


THE   HEATING   AND  VENTILATING   OF   SHIPS. 


lost  by  conduction  through  the  walls  of  the  room,  by  air  cur- 
rents, etc.,  if  T  is  taken  as  the  temperature  to  which  the  air  in 
the  room  would  otherwise  fall  in  any  given  time.  This  is 
dealt  with  farther  on,  when  explaining  how  the  heat  lost  from 
the  room  is  made  up. 

Another  point  that  should  be  mentioned  is  the  effect  of  the 
velocity  of  the  flow  of  water  through  the  pipes.  The  velocity, 
of  the  flow  of  air  over  radiators,  etc.,  and  its  effect,  will  be 
dealt  with  when  discussing  the  heating  of  air,  but  it  may  be 
mentioned  that,  as  is  well  known  to  marine  engineers,  the 
rate  of  delivery  of  heat  from  a  hot-water  pipe  increases  with 
the  velocity  of  the  water,  up  to  a  certain  figure.  The  writer 
believes  that  experiments  have  not  yet  been  made  with  a  view 
of  showing  what  the  critical  figure  is,  but,  within  the  limits 
of  ordinary  hot-water  heating  appliances,  every  increase  of 
the  rate  of  flow  tends  to  increase  the  heat  delivered. 

Another  point  should  be  mentioned  in  connection  with  both 


FIG.   II. — korting's  radiator  for  steam  or  hot  water,  consisting  of 

PARALLEL      HORIZONTAL     RIBBED      PIPES,      CONNECTED     TO      HEADERS     AT 
EACH    END. 


FORMS    OF    HEATING   APPARATUS    WITH    HOT    WATER. 


157 


FIG.    10. ROYLE    RADIATOR    ON    SIR    THOMAS    LIPTON's   YACHT.       ROW'S    TUBES 

GIVE     FLEXIBILITY    AND     LARGER     HEATING     SURFACE. 


steam  and  hot-water  heating.  The  radiator  has  been  de- 
veloped because  of  the  necessity  of  arranging  a  large  surface 
of  pipe  within  a  comparatively  small  compass,  and  in  such  a 
form  that  it  can  be  fixed  in  rooms,  etc.,  without  inconvenience. 
Forms  of  the  radiator  are  shown  in  Figs.  9,  10  and  II.  As 
will  be  seen,  the  radiator  is  simply  a  pipe  arranged  in  a  par- 
ticular manner.  A  favorite  form  consists  of  a  number  of 
vertical  columns,  each  column  consisting  *of  a  single  pipe,  a 


158 


THE    HEATING    AND   VENTILATING    OF    SHIPS. 


loop  of  pipe,  or  two,  three  or  four  columns ;  the  whole  of  the 
columns  being  held  together  and  standing  on  feet,  raising 
them  a  few  inches  above  the  floor.  The  pipes  forming  the 
columns  are  arranged  in  more  or  less  ornamental  form,  and" 
their  outside  surfaces  are  given  the  forms  shown,  in  order  to 
present  as  large  a  surface  as  possible  to.  the  air  which  passes 
through  them  and  over  them.  As  will  be  explained  when 
dealing  with  warming  air  by  means  of  radiators,  special  ar- 
rangements  are   sometimes   made   to   direct  the   air  over  the 


FIG.    12. RADIATOR    FOR    HOT    WATER    OR    STEAM. 

COMPANY. 


NATIONAL    RADIATOR 


whole  of  the  surface  of  the  radiator  before  passing  into  the 
room. 

The  columns  of  which  the  radiators  are  composed  are  ar- 
ranged with  channels  at  top  and  bottom,  which,  when  the 
columns  are  assembled  together,  form  pipes  for  the  steam  or 
water,  both  communicating  with  the  tubular  spaces  inside  the 
columns.  Also,  as  will  be  seen  from  the  drawings,  it  is  ar- 
ranged in  nearly  all  forms  of  radiators  that  connection  can 
be  made  to  either  end  of  the  channels  referred  to,  at  top  or 
bottom,  so  that  the  hot  water  or  steam  can  be  brought  to 


FORMS    OF    HEATING    APPARATUS    WITH    HOT    WATER.         159 

either  end  of  the  radiator,  and  where  a  return  connection  is 
made,  that  also  can  be  taken  from  either  end.  This  is  the 
usual  form,  but  it  will  be  understood  that  any  design  may  be 
arranged  that  will  provide  for  the  connection  between  the 
water  or  steam  supply  and  the  radiator,  and  for  the  circula- 
tion of  the  steam  or  water  through  the  individual  columns, 
and  for  the  connection  to  the  return,  where  there  is  one. 


FIG.  13. BATTERY  Of  COLONIAL  RADIATORS  FIXED  VERTICALLY. 

Radiators  are  arranged  to  go  into  all  sorts  of  confined 
spaces,  such  as  cabins.  Figs.  12  and  13  show  the  Colonial 
radiator,  made  by  the  National  Radiator  Company,  of  Chicago 
and  London,  which  has  been  fitted  on  board  H.  M.  S.  King 
Edward  VII.  It  is  arranged  to  be  fixed  on  brackets,  secured 
to  bulkheads,  at  any  convenient  height,  as  shown.  One  method 
of  fixing  to  walls  is  shown  in  Fig.  14.  Its  great  feature  is,  as 
will  be  seen,  the  fact  that  it  will  lie  close  to  a  bulkhead,  or  to 
the  ship's  side.  It  is  made  in  three  sizes,  respectively,  29,  23 
and  1634  inches  long,  all  13*4  inches  high,  and  2%  inches  deep. 
When  fixed  a  little  way  from  the  bulkhead,  the  space  occupied 
is  very  small,  and  it  can  be  built  into  any  convenient  form, 
several  of  any  size  being  connected  together  by  right  and 
left-hand  threaded  npples,  and  arranged  side  by  side  vertically 


160 


THE   HEATING   AND  VENTILATING   OF   SHIPS. 


or  horizontally,  as  may  be  convenient.  Thus,  a  number  of 
them  may  be  arranged  under  the  seats  around  the  stern  of 
a  ship,  or  in  any  other  situation. 

A  form  of  radiator  that  is  a  great  favorite  in  hospitals  is 
fitted  with  hinges  at  one  end,  the  valves  passing  through  the 


FIG.     14. SIDE    OF     SINGLE-LOOP    RADIATOli. 

NATIONAL      RADIATOR      COMPANY. 

hinges  so  that  it  can  be  turned  back  against  the  wall  or 
brought  forward  into  the  room.  It  appears  to  the  writer  that 
this  form  would  also  be  useful  for  cabins  and  other  confined 
spaces  on  board  ship.    It  is  shown  in  Fig.  15. 

Radiators  can  be  arranged  to  suit  any  style  of  decoration, 
and   practically  to   fit   any  sj-ace.     They  may  be  painted  to 


FORMS    OF    HEATING    APPARATUS    WITH    HOT    WATER. 


161 


match  the  decorations  of  the  cabin  or  saloon,  and  they  are  fre- 
quently ornamented  in  various  ways,  the  castings  from  which 
they  are  formed  having  an  ornamental  pattern  upon  them, 
the  decorative  work  being  afterwards  added  by  artists.  In 
the  hot-water  radiator  it  is  usual  to  bring  the  connection  of  the 
supply  pipe  to  the  top  of  the  radiator,  and  that  from  the  re- 


FIG.     15. SWINGING     RADIATOR    OF     NATIONAL     RADIATOR     COMPANY. 

THE    VALVES    ARE    IN    THE    HINGES. 


turn  pipe  to  the  bottom.  An  air  cock  or  valve  should  be  fitted 
on  each  radiator  at  the  end,  away  from  the  supply  service  and 
at  the  top,  and  it  should  be  seen  that  it  is  always  in  order. 
For  positions  where  appearance  is  not  of  consequence,  as  in 
the  forecastle,  and  in  emigrants'  quarters,  the  radiator  may 
take  the  form  of  a  grid  of  iron  pipes. 
There  is  another  system  of  hot-water  heating  that  has  been 


162  THE    HEATING    AND   VENTILATING   OF    SHIPS. 

fixed  in  some  yachts,  known  as  the  Reck,  which  is  the  inven- 
tion of  a  Danish  engineer  of  that  name.  In  this  system  the 
heating  effect  of  steam  directly  injected  into  a  body  of  water 
is  combined  with  the  effect  of  the  same  steam  passing  around 
a  body  of  water,  on  the  lines  of  the  feed-water  heater.  There 
is  a  boiler  for  generating  steam,  fixed  at  the  lowest  part  of  the 
system  (it  would  be  in  the  stoke  hold  on  board  ship),  and  a 
little  above  the  boiler  is  an  apparatus  termed  by  the  inventor  a 
"reheater,"  a  device  similar  to  a  feed-water  heater.  At  the 
top  of  the  system  is  the  principal  heating  apparatus  for  the 
water.  It  is  termed  by  the  inventor  the  "circulator."  There 
is  the  usual  expansion  tank  above  the  circulator,  and  imme- 
diately below  the  circulator  is  another  apparatus  called  the 
condenser.  Steam  is  taken  directly  from  the  boiler  by  a  pipe 
to  the  reheater,  where  it  passes  around  the  pipes,  through 
which  the  return  water  from  the  circulating  system  is  passing, 
and  another  pipe  is  taken  from  the  top  of  the  reheater  to  a 
point  above  the  circulator.  This  pipe  is  curved  around  at  the 
top  into  an  inverted  U,  and  is  brought  into  the  top  of  the  cir- 
culator. From  the  lower  part  of  the  expansion  tank  a  pipe 
passes  to  the  upper  part  of  the  circulator,  and  a  second  pipe 
is  also  taken  from  the  lower  part  of  the  expansion  tank  along 
the  upper  portion  of  the  upper  rooms,  or  the  upper  deck,  to  be 
warmed,  and  from  this  the  circulating  pipes  to  the  radiators 
are  taken.  The  expansion  tank  is  fitted  with  a  cover ;  a  second 
pipe  passes  from  its  upper  part  to  the  condenser,  and  another 
pipe  from  the  condenser  to  the  water  space  of  the  boiler.  The 
return  pipe  of  the  circulator  system,  which  passes  along  the 
lower  rooms,  or  the  lower  deck,  to  be  heated,  is  connected  to 
the  reheater,  a  second  pipe  conveying  the  heater  water  to  the 
circulator. 

The  working  of  the  arrangement  is  as  follows :  The  cir- 
culator, being  full  of  water  which  has  returned  from  heating 
the  radiators,  is  heated  by  steam  delivered  directly  from  the 


FORMS    OF    HEATING    APPARATUS    WITH    HOT    WATER.         163 

boiler  through  the  pipe  mentioned.  When  heated,  it  over- 
flows into  the  expansion  tank  and  thence  to  the  pipe  forming 
the  main  flow  pipe  of  the  hot-water  circulating  system. 
Branch  pipes  connect  the  main  flow  pipe  with  the  return  pipe 
at  the  bottom,  and  radiators  are  connected  to  these  branch 
pipes  in  a  manner  which  may  be  compared  to  the  shunt  system 
in  electrical  work.  The  radiators  are  bridged  or  shunted 
across  a  portion  of  the  vertical  pipe.  The  heated  water,  hav- 
ing passed  down  through  the  vertical  pipes  and  the  radiators, 
returns  to  the  reheater  by  the  return  pipe,  is  there  heated  by 
the  sfeam  circulating  around  the  pipes  through  which  the 
water  is  passed,  and  thence  again  commences  its  outward 
journey,  passing  up  the  pipe  to  the  circulator^  where  it  is 
further  heated  by  steam,  and  so  on. 

The  condenser  is  similar  to  the  usual  surface  condenser, 
with  which  marine  engineers  are  familiar.  It  consists  of  the 
ordinary  cylinder,  with  a  series  of  tubes,  arranged  either  in  a 
vertical  or  horizontal  position  as  may  be  convenient.  This 
device  condenses  the  steam  which  is  delivered  in  the  circu- 
lator, but  which  is  not  fully  employed  in  heating  the  water  for 
the  circulation  system,  and  which  finds  its  way  through  the 
pipe  into  the  expansion  tank,  and  thence  rising  in  bubbles,  in 
the  well-known  manner,  passes  out  of  the  top  of  the  expan- 
sion tank  by  the  pipe  leading  to  the  condenser.  It  is  con- 
densed by  the  flow  of  the  water  coming  from  the  reheater, 
the  condensed  water  being  carried  off  by  a  pipe  to  the  water- 
space  in  the  boiler. 

It  will  be  noticed  that  the  water  receives  heat  from  the 
steam  at  three  places;  in  the  circulator  itself  by  direct  con- 
tact, in  the  reheater  and  in  the  condenser.  Further,  the  de- 
livery of  steam  from  the  circulator  into  the  closed  expansion 
tank,  by  setting  up  a  certain  pressure  above  the  water  in  the 
expansion  tank,  causes  the  water  to  run  freely  in  the  circu- 
lating   system,    quite    apart    from    the    circulation    caused    by 


164  THE    HEATING   AND  VENTILATING  OF   SHIPS. 

difference  of  temperature,  etc.  The  water-supply  service  is 
usually  connected  to  the  expansion  tank  with  a  ball  cock,  in 
the  usual  way,  cold  water  being  added  to  the  system  when  re- 
quired and  passing  directly  into  it. 

The  advantage  claimed  for  the  Reck  system  is,  that  heat 
will  be  got  up  very  much  more  quickly  by  its  aid  than  with 
the  ordinary  system  of  hot-water  service  that  has  been  ex- 
plained. On  the  other  hand,  it  is  rather  more  complicated 
than  the  simple  hot-water  system,  but  the  apparatus  of  which 
it  is  composed  should  present  no  difficulty  to  marine  engi- 
neers. The  main  source  of  heat  is  usually  a  boiler  on  shore, 
and,  in  places  where  there  is  no  other  steam  supply,  can,  of 
course,  be  steam  from  the  ship's  boilers,  or  the  exhaust  steam 
from  the  engines  or  auxiliaries,  or  any  other  convenient 
source. 

HEATING    BY    STEAM. 

The  arrangements  for  heating  by  steam  are  practically  the 
same  as  those  for  heating  by  hot  water,  with  a  few  modifica- 
tions, due  to  the  difference  between  the  flow  of  steam  and  hot 
water,  and  to  the  necessity  for  draining  the  condensed  steam 
out  of  the  heating  appliances.  The  source  of  heat  may  be  the 
same  as  with  hot  water,  but  arranged,  where  it  is  a  boiler,  to 
generate  steam  at  low  pressure,  instead  of  merely  to  heat  the 
water.  On  board  ship,  steam  from  the  boilers  is  usually  em- 
ployed, reduced  to  the  required  pressure  by  one  of  the  well- 
known  forms  of  reducing  valve.  On  shore,  pressures  of  about 
5  pounds  per  square  inch  gage  are  employed,  and  from  that 
downwards.  A  very  favorite  form  of  heating  is  by  exhaust 
steam,  at  below  atmospheric  pressure.  As  marine  engineers 
hardly  need  reminding,  the  volume  of  steam  and  its  latent 
heat  per  pound  increase  rapidly  at  pressures  below  the  atmos- 
phere, and  in  some  forms  of  steam  heating,  pressures  as  low 
as  i  pound  absolute  per  square  inch,  or  even  less,  are  em- 
ployed.   On  board  ship,  pressures  of  from  15  to  25  pounds  are 


HEATING   BY    STEAM.  165 

more  frequent,  because  of  the  inconvenience  of  reducing  to 
much  lower  pressures. 

Heating  by  steam  also  differs  from  heating  by  hot  water,  in 
the  temperature  of  the  heating  appliance.  Thus,  with  15 
pounds  gage  pressure  the  temperature  of  steam  is  about  2500 
F. ;  at  5  pounds  gage  pressure  it  is  228°  F. ;  while,  as  explained, 
the  usual  temperature  of  the  hot  water  employed  in  heating 
appliances  is  in  the  neighborhood  of  1700  F.  With  exhaust 
steam  below  atmospheric  pressure,  practically  the  same  tem- 
peratures are  obtainable  as  with  hot  water,  and  that  is  another 
advantage  in  its  favor,  apart  from  its  economy.  The  tempera- 
ture of  steam  at  6  pounds  absolute  is  170°  F.,  and  the  latent 
heat  is  9947  B.  T.  U.  per  pound;  while  at  15  pounds  gage 
pressure  it  is  only  938  units,  and  at  25  pounds  gage  pressure 
only  926.  The  higher  temperatures  of  the  heating  appliances 
are  in  favor  of  the  liberation  of  a  larger  quantity  of  heat  per 
square  foot  of  the  heating  appliances  per  hour,  because  of  the 
larger  difference  of  temperature  between  the  surface  of  the 
heating  appliance  and  that  of  the  surrounding  air,  and  again 
because  of  the  peculiar  feature  mentioned  above  of  the  rapid 
increase  of  the  rate  at  which  heat  is  liberated,  as  the  difference 
of  temperature  increases. 

On  the  other  hand,  however,  there  are  grave  objections  to 
heating  by  steam,  and  those  objections  have  led  to  the  adoption 
of  hot  water  heating  appliances  on  shore  to  a  very  much  larger 
extent  than  steam  heating.  The  objections  are  that  the  steam 
heating  appliances  are  not  so  easily  controlled  as  the  hot  water 
appliances,  and  also  there  is  the  constant  danger  of  the  tem- 
perature of  the  heating  appliance  rising  to  a  figure  which 
causes  it  to  produce  a  smell,  referred  to  by  heating  engineers 
usually  as  that  of  burnt  air.  It  is  probable  that  this  is  largely 
burnt  dust.  There  is  also  probably  some  action  going  on 
between  the  highly  heated  surface  of  the  radiator  and  the  air, 
that  is  not  present  with  lower  temperatures.    Where  the  tern- 


166 


THE    HEATING    AND   VENTILATING   OF    SHIPS. 


perature  of  the  heating  apparatus  is  maintained  at  about  that 
cf  boiling  water,  at  ordinary  atmospheric  pressures,  steam 
heating  appliances  have  presented  no  difficulty  whatever,  but 
steam  pressures  are  sometimes  not  easily  controlled.  Where 
a  number  of  appliances  are  worked  from  the  same  source  of 
heat,  and  the  supply  of  steam  is  shut  off  to  any  considerable 
portion  of  them,  unless  the  supply  at  the  source  is  also  re- 
duced, marine  engineers  will  hardly  need  reminding,  the  pres- 


FIG.     16. TWO-PIPE    SYSTEM,     LOW-PRESSURE    STEAM. 


sure  of  the  steam — and  therefore  its  temperature — in  the 
remaining  portion  will  rise,  and  the  results  mentioned  will  be 
produced. 

The  heating  appliances  used  with  steam  heating  are  the 
same  as  for  hot  water  heating.  In  fact,  many  makers  list  their 
radiators  as  applicable  for  steam  or  hot  water.  Pipes,  of 
course,  can  also  be  used  for  steam  or  hot  water,  providing  the 
sizes  are  in  accordance.  One  or  two  points  of  difference  have 
to  be  noted  between  the  treatment  of  the  two  systems.  With 
hot  water  distribution  systems,  the  pipes  are  sloped  where  they 
are  out  of  the  vertical,  so  that  the  water  will  drain  towards 
the  boiler.  With  steam  the  pipes  are  sloped  in  the  opposite 
direction,  in  order  that  any  condensed  water  that  is  formed 


HEATING    BY     STEAM. 


167 


may  be  carried  with  the  steam  in  the  direction  in  which  it  is 
going,  and  may  be  driven  out  by  the  valve  provided  for  it. 
Air  is  lighter  than  water,  and  therefore,  as  was  explained,  air 
cocks  are  to  be  fitted  at  the  highest  points  of  the  service  and 
at  the  tops  of  radiators.  Air  is  heavier  than  steam,  arfd 
therefore  works  its  way  downwards,  and  air  cocks  are  there- 
fore fitted  at  the  bottom  portion  of  radiators  and  in  similar 
positions. 


FIG.     17. ONE-PIPE    CIRCUIT     SYSTEM,     LOW-PRESSURE     STEAM. 


There  are  practically  two  systems  of  distribution  of  steam 
to  the  heating  appliances,  known  respectively  as  the  two-pipe 
and  the  single-pipe  systems.  In  the  two-pipe  system  the  steam 
is  carried  to  the  radiator,  and,  with  the  condensed  water  that 
is  formed,  is  carried  away  to  some  receptacle,  from  which  it  is 
pumped  to  the  boiler,  hot  wells,  etc.  On  the  one-pipe  system 
the  steam  is  merely  delivered  to  the  radiator,  and  the  con- 
densed water  that  is  formed  is  carried  off  from  the  radiator 
with  the  air  that  is  driven  out.  Figs.  16  and  17  show  the  two- 
pipe  and  one-pipe  systems  as  usually  arranged.  It  is  usual 
with  steam  systems  to  have  lines  of  air  pipes  connected  to  the 


168  THE   HEATING   AND  VENTILATING  OF   SHIPS. 

radiators,  delivering  the  air  that  may  have  worked  into  the 
system  with  the  steam,  and  that  has  to  be  driven  out.  This 
air  is  forced  by  the  pressure  of  the  steam  out  of  the  radiator 
through  the  air  lines  and  discharged  at  a  point  where  it  will 
be  harmless.  Where  exhaust  steam  is  employed,  it  is  usual  to 
employ  also  a  vacuum  pump  on  the  return  pipes  of  the  system, 
to  bring  the  condensed  steam  and  air  back  from  the  radiators. 

KORTING'S     LOW-PRESSURE     STEAM-HEATING     APPARATUS. 

Messrs.  Korting  Brothers,  of  Germany,  who  have  made  a 
close  study  of  heating  apparatus  generally,  have  worked  out  a 
special  system  of  low-pressure  steam  heating,  which  will  be 
described.  The  steam  is  generated  in  a  special  boiler  at  a 
pressure  not  exceeding  \x/2  pounds  per  square  inch,  but  pre- 
sumably ordinary  steam  can  be  employed,  providing  that  the 
reducing  valve  is  arranged  to  lower  the  pressure  to  that  figure. 
The  very  low  pressure  of  operation  is  provided  to  meet  the  ob- 
jection mentioned  above,  to  the  smell  that  sometimes  arises 
from  steam-heating  apparatus,  owing  to  the  burnt  dirt  and 
burnt  air  with  apparatus  at  high  temperatures.  A  diagram  of 
this  is  shown  in  Fig.  18. 

For  use  with  exhaust  steam,  an  apparatus  is  employed  in 
which  the  reducing  valve  is  controlled  by  a  lever,  operated  by  a 
float  working  against  a  spring,  the  position  of  the  float  in  the 
vessel  being  regulated  by  the  pressure  of  the  steam  supply. 
When  the  pressure  of  the  steam  supply  rises,  the  water  in  the 
vessel  in  which  the  float  moves  is  driven  downwards  through 
the  pipe  at  the  bottom  into  another  vessel  at  the  side,  whose 
position  can  be  adjusted,  the  float  then  falling  and  partially 
closing  the  valve ;  the  reverse  operation  taking  place  if  the 
steam  pressure  falls.  Where  steam  is  supplied  from  the  special 
boiler,  the  draft  of  the  furnace  is  controlled  by  the  tempera- 
ture of  the  steam;  a  slight  increase  of  temperature  partially 
closing  the  furnace  damper,  and  vice  versa.     It  is  doubtful 


A   COMBINED   AIR   AND   STEAM    RADIATOR. 


169 


whether,  under  ordinary  conditions  of  sea-going  ships,  such 
apparatus  would  be  desirable,  but  in  sailing  ships  and  in  yachts, 
and  in  some  classes  of  ships,  such  as  whalers,  sealers,  etc., 
where  the  travel  of  the  ship  at  times  is  not  great,  it  might  be 
convenient  to  have  an  apparatus  of  this  kind. 


■.■■■■■  vj 


HSi 


A    COMBINED  AIR    AND   STEAM    RADIATOR. 


Messrs.  Korting  have  also  introduced  a  radiator,  in  which 
the  steam  is  cooled  by  the  presence  of  a  certain  quantity  of  air. 
Steam,  it  will  be  remembered,  unless  it  is  supplied  below  at- 
mospheric pressure,  must  be  at  or  above  2120  F.,  and  this  is  a 
somewhat  high  temperature  under  certain  conditions.  The 
temperature  may  be  lowered  by  employing  the  partial  vacuum 
method,  but  it  is  also  claimed  by  Messrs.  Korting  that  it  is 
lowered  in  their  special  radiators  by  the  addition  of  air. 

The  radiator  is  of  the  usual  form,  with  a  steam  pipe  running 
along  the  bottom  of  the  sections,  and  at  each  section  a  steam 
nozzle  enters  the  pipe.     The  admission  of  steam  is  controlled 


170  THE     HEATING     AND    VENTILATING    OF    SHIPS. 

by  the  valve  at  the  entrance  to  the  radiator,  in  the  usual  way, 
and  the  steam  passing  out  of  the  nozzle  is  allowed  to  draw  air 
in  with  it,  on  the  well-known  injector  principle.  It  is  claimed 
that  the  steam  mixes  with  the  air,  the  former  being  cooled 
thereby,  and  the  outside  temperature  of  the  radiator  being  con- 
sequently lowered,  the  air  and  steam  circulating  together,  and 
the  condensed  steam  being  drawn  off  in  the  usual  way. 

HEATING    BY    ELECTRICITY. 

All  electrical  heating  apparatus  is  based  upon  the  fact  that, 
when  an  electric  current  passes  through  a  conductor,  heat  is 
liberated  in  direct  proportion  to  the  resistance  of  the  con- 
ductor and  to  the  square  of  the  strength  of  the  current.  The 
formula  is  //  =  tRO ' ,  where  II  is  the  quantity  of  heat  liber- 
ated in  time  t,  C  is  the  current  strength  in  amperes,  and  R  is 
the  resistance  of  the  conductor  in  ohms.  The  formula  may 
also  be  written, 

EH 

II  =  ECt,  orH= , 

R 

where  E  is  the  difference  of  pressure  in  volts  at  the  terminals 
of  the  conductor.  Connection  is  made  with  the  thermal  system 
by  the  fact  that  H  is  expressed  in  watts,  the  electrical  unit  of 
the  rate  of  expenditure  of  energy,  and  that  17.58  watts  equals 
one  B.  T.  U.     This  matter  is  referred  to  again  further  on. 

Heating  takes  place  in  all  forms  of  electrical  apparatus,  in 
cables,  in  the  conductors  forming  part  of  the  coils  of  dynamos, 
motors,  etc.,  and  also  in  all  forms  of  electric  lamps.  But,  in 
the  case  of  cables  and  conductors  forming  parts  of  dynamos 
and  motors,  the  heat  is  kept  as  low  as  possible,  and  in  the  case 
of  lamps,  the  great  object  striven  for  is  to  obtain  as  large  a 
conversion  as  possible  of  the  heat  waves  into  light  waves-  In 
heating  apparatus  the  great  object  to  be  attained  is  of  course 
heat,  and  therefore  all  electrical  heating  apparatus  is  designed 


HEATING    BY     ELECTRICITY.  171 

with  a  high  resistance,  so  that  as  large  a  quantity  of  heat  shall 
be  liberated  as  possible,  within  a  given  space. 

Electrical  heating  apparatus  has  so  far  divided  itself  into  two 
main  branches,  the  luminous  and  non-luminous.  Luminous 
electrical  heating  apparatus  is  merely  an  extension  of  the  well- 
known  electric  incandescent  lamp.  The  current  passing 
through  the  filament  of  such  a  lamp,  it  will  be  remembered, 
first  liberates  heat ;  and  if  the  current  is  not  of  a  certain  definite 
strength,  only  heat  will  be  liberated,  and  the  lamp  filament  re- 
mains black,  but  it  is  still  giving  out  some  heat,  though  the 
pressure  is  too  low  for  the  lamp  in  question.  When  the  pres- 
sure and  the  temperature  are  a  little  higher,  the  lamp  becomes 
red,  a  larger  amount  of  heat  is  given  out,  and  the  small  quan- 
tity of  light  possessed  by  the  red  rays.  As  the  pressure  and 
the  current  are  increased,  the  lamp  becomes  gradually  brighter, 
finally  assuming  the  well-known  yellow  tinge,  or,  if  allowed, 
becoming  white  hot.  In  all  cases,  however,  whatever  the  color 
of  the  filament,  and  whatever  the  temperature  to  which  it  may 
be  raised,  the  whole  of  the  electrical  energy  delivered  to  it 
eventually  becomes  heat,  and  is  delivered  to  the  air  of  the 
room  in  which  the  lamp  is  fixed. 

Under  ordinary  circumstances,  the  carbon  filament  incan- 
descent lamp  converts  from  about  3  to  5  percent  of  its  heat 
into  light,  but  the  light  rays  are,  so  far  as  is  known  at  present, 
reconverted  into  heat  in  the  room.  The  action  is  the  same  as 
the  action  of  the  sun's  rays  upon  a  greenhouse.  It  is  well 
known  that  it  is  the  light  rays  of  the  sun  which  cause  the 
heating  effect  in  the  greenhouse,  very  much  more  largely  than 
the  heat  rays.  Glass  is  transparent  to  light  rays,  and  they 
pass  through  the  glass  into  the  greenhouse,  as  through  the 
glass  of  the  incandescent  electric  lamp,  and  are  converted  into 
heat  waves  on  the  other  side.  In  the  case  of  the  greenhouse, 
a  •  glass  resists  the  passage  of  heat  rays  through  it,  the  con- 
verted light  rays  cannot  escape  so  easily  as  they  passed  into 


172  THE    HEATING    AND    VENTILATING   OF    SHIPS. 

the  greenhouse,  and  the  temperature  is  raised.  Similarly,  the 
light  rays  from  the  incandescent  electric  lamp  become  heat 
rays  on  passing  out  into  the  room,  and  the  remainder  of  the 
electrical  energy  delivered  to  the  filament  becomes  heat  within 
the  filament  globe,  and  heats  the  globe  in  the  well-known 
manner,  the  heat  being  then  transmitted  to  the  air  of  the 
room  in  the  usual  way. 

Consideration  of  the  two  types  of  heaters,  luminous  and 
non-luminous,  makes  it  evident  that  where  continuous  service 
is  desired,  a  heater  which  depends  on  the  setting  up  and  circu- 
lation of  air  currents  passing  through  it  gives  the  best  results. 
If  immediate  heat  is  required  the  luminous  radiator  is  prac- 
tically instantaneous.  It  heats  the  person  rather  than  the  air 
in  the  room,  the  latter  being  warmed  only  indirectly  from  the 
heated  surfaces  on  which  the  rays  from  the  radiator  may  fall. 
For  immediate,  localized  heat,  for  warming  the  person,  it  has 
no  superior,  and  this  fact  often  permits  the  use  of  electric  heat 
where  it  would  otherwise  be  far  too  expensive.  This  distinc- 
tion should  be  clearly  emphasized  if  an  intelligent  application 
of  the  two  forms  is  to  be  made. 

ELECTRIC     HEATING    APPLIANCES     ON     SHIPBOARD. 

Recognizing  the  vast  possibilities  in  the  application  of  elec- 
tricity to  heating,  many  manufacturing  electric  companies  have 
developed  a  variety  of  special  devices  which  have  already  won 
such  favor  that  it  seems  certain  they  will  be  as  commonly 
used  as  the  incandescent  lamp.  A  ship's  lighting  plant,  usually 
of  more  than  ample  capacity  for  its  intermittent  load,  offers  at 
once  an  available  source  of  supply,  which,  utilized  for  cooking 
in  the  galley  or  heating  in  the  staterooms,  would  provide 
numerous  real  and  profitable  conveniences  with  small  increase 
in  cost. 

The  electric  heater  is  ideal  for  stateroom  use.  It  is  com- 
pact and  neat  in  appearance,  and  easily  turned  on  and  off,  thus 


ELECTRIC    HEATING    APPLIANCES    ON    SHIPBOARD.  173 

admitting  of  regulation  of  temperature  for  each  individual 
room.  It  is  connected  by  simple  wiring,  which  is  more  flexible 
than  steam  piping.  The  wires  take  little  space  and  can  be  run 
anywhere,  while  steam  pipes  are  bulky  and  apt  to  leak,  and 


FIG.    19. — GLOW-LAMP    RADIATOR    AND    METER.        SAPPLIES,    LTD. 

necessarily  heat  the  spaces  through  which  they  pass.  It  is  safe 
to  say  that  the  electric  radiator,  although  deriving  its  heat  in- 
directly from  steam,  is  no  less  efficient,  when  the  losses  due  to 
leakage  and  radiation  are  taken  into  consideration. 


174 


THE    HEATING    AND    VENTILATING    OF    SHIPS. 


FIG.     20. GLOW-LAMP     RADIATORS    WITH     METERS    ATTACHED. 

GLOW-LAMP   RADIATORS. 

Forms  of  what  are  termed  glow-lamp  radiators  are  shown 
in  Figs.  19  and  20.  They  are  now  well  known,  and  consist  of 
from  two  to  four  specially  made  carbon  filament  incandescent 
lamps,  usually  9  inches  long,  with  a  single  horseshoe  filament, 
approximately  double  the  length  of  the  lamp;  the  two,  three 


FIG.    21.— BRITISH    THOMSON-HOUSTON    EDISON    RADIATOR    LAMP. 


GLOW-LAMP     RADIATORS. 


175 


or  four  lamps  being  held  in  some  ornamental  fitting,  usually 
with  a  reflector  behind  them,  and  arranged  to  throw  the  whole 
of  the  rays  from  the  lamp  out  into  the  room.  The  apparatus 
is  fitted  with  switches,  arranged  to  connect  one,  two,  three  or 
four  lamps,  as  required,  so  that  the  heat  delivered  to  the  room 
may  be  regulated  within  these  limits.  Fig.  21  shows  one  of 
the  lamps,  by  the  British  Thomson-Houston  Company,  and 


fig.   22. — king  edward's  quarters  on   the  royal   yacht  victoria   and 

ALBERT. 


Fig.  22  shows  King  Edward's  cabin  on  board  the  royal  yacht, 
heated  by  one  of  Dowsing's  luminous  radiators. 

Some  makers  are  also  providing  electric  radiators  with  glow 
lamps,  of  the  pattern  described,  inside  of  various  inclosures, 
the  appearance  being  very  much  the  same  as  that  of  the  non- 
luminous  radiators  or  convectors  described  further  on.  In  one 
form,    two   or   four  lamps   are   inclosed    inside   a   cylindrical 


176  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

copper  or  brass  case,  with  perforations,  the  whole  apparatus 
standing  a  little  off  the  floor.  The  idea  here  is  that  the  air 
passes  under  the  apparatus,  up  over  the  lamps,  and  out  through 
the  perforations  at  the  top  and  the  side.  This  is  shown  in  Fig. 
23.  Other  forms  are  almost  copies  of  the  non-luminous  ra- 
diators. They  are  rectangular  in  form  and  inclose  two  or  four 
lamps  inside  a  framework,  raised  slightly  from  the  floor  by 
feet,  and  the  front  of  the  apparatus  being  closed  by  slips  of 
ruby  glass,  the  effect  is  pretty.  There  are  also  other  forms  of 
this  arrangement  on  something  the  same  lines.  The  British 
Prometheus  Company  has  also  introduced  glow-lamp  radiators, 
in  which  the  lamps  are  maintained  at  only  red  heat. 

THE    EFFECT    OF   THE    LIGHT    RAYS. 

It  should  perhaps  be  mentioned,  en  passant,  that  it  is  claimed 
by  makers  of  glow  lamp  radiators  that  the  light  rays  issuing 
from  the  glow  lamps  have  an  important  office,  and,  in  the 
writer's  view,  this  is  strictly  correct.  It  will  be  remembered 
that  white  light  is  made  up  of  the  different  colors  forming 
the  solar  spectrum,  as  we  see  it  in  the  rainbow,  and  that  the 
rays  forming  the  different  colors  have  different  wave  lengths, 
different  periods  and  different  properties.  Thus,  the  red  rays 
have  comparatively  long  waves,  about  double  the  length  of  the 
violet  rays,  and  their  property  is  principally  heating.  The 
violet  rays  at  the  opposite  end  of  the  spectrum  have  compara- 
tively short  waves,  and  the  principal  property  is  actinic  or 
chemical.  It  is  the  violet  rays  which  are  most  useful  in 
photography. 

Between  the  violet  and  the  red  is  a  long  range  of  rays  of 
different  colors,  whose  properties  vary,  most  of  them  having 
been  thoroughly  worked  out.  Apparently  the  yellow  rays  are 
those  which  do  most  in  the  direction  of  furnishing  light. 
Glass  and  some  other  substances,  the  human  skin  of  the  white 
man  being  one  of  them,  according  to  some  experiments  that 


THE    EFFECT    OF    THE    LIGHT    RAYS. 


177 


have  been  made,  are  apparently  transparent  to  the  yellow  and 
green,  and  some  of  the  other  waves  at  that  end  of  the  spec- 
trum, the  waves  after  passing  through  the  glass  or  the  skin 
being  transformed  into  heat  waves.  This  has  been  mentioned 
as  the  cause  of  the  heat  produced  in  greenhouses  when  the 
sun  is  bright. 


FIG.     23. GLOW-LAMP     RADIATOR. 


Mr.  Dowsing's  work  also  in  connection  with  the  use  of  the 
electric  glow  lamp,  of  the  type  described  for  heating,  in  con- 
nection with  therapeutics,  has  shown  that  the  light  waves 
have  a  very  important  effect  upon  the  human  body.  The  elec- 
tric light  bath  is  now  well  known,  and  its  effects  are  produced, 
it  is  believed,  by  the  light  rays  issuing  from  the  lamps,  and 


178  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

not  by  the  heat  rays.  Another  peculiar  feature  about  them 
is,  according  to  Mr.  Dowsing,  that  the  pigment  under  the  skin 
of  the  black  man  is  not  transparent  to  the  light  rays.  Thus, 
one  cannot  give  a  black  man  an  electric  light  bath.  It  does 
him  no  good.  This  would  apparently  be  the  reason  why  the 
black  man  can  stand  the  sun's  rays.  It  is  not  the  heat  rays 
which  trouble  the  white  man  so  much  as  the  light  rays,  which 
pass  through  his  skin,  there  becoming  heat ;  while  they  do  not 
pass  through  the  pigment  in  the  black  man's  skin. 

It  will  be  seen  that  this  has  an  important  bearing  upon  the 
question  of  the  warming  of  living  rooms,  whether  on  shore 
or  afloat.  Everyone  is  familiar  with  the  prejudice,  as  it  is 
thought  to  be,  in  favor  of  a  bright,  glowing  fire;  and  it  is 
not  the  fire  of  red  coals  that  is  liked,  but  one  in  which  white 
or  yellow  flames  are  dancing  around  the  grate  bars.  If  the 
above  reasoning  is  correct,  this  tendency,  like  so  many  others, 
is  well  founded,  and  the  light  rays  have  an  important  func- 
tion in  the  matter  of  heating.  If  so,  also,  the  luminous  radiator 
should  have  an  important  office  to  fulfil  in  the  problem  of 
heating  saloons,  cabins,  etc.  In  the  writer's  experience,  when 
away  at  sea,  nothing  is  more  pleasant  than  a  bright  light  in 
the  mess  or  in  one's  cabin,  and  a  bright  radiator  will  probably 
have  the  same  effect. 

The' lamps  in  question  consume  one-quarter  of  a  kilowatt 
per  hour.  That  is  to  say,  with  the  usual  ioo-volt  service  em- 
ployed on  board  ship,  each  lamp  would  take  2^2  amperes ;  a 
radiator  of  two  lamps,  suitable  for  a  small  cabin,  5  amperes; 
one  of  four  lamps,  suitable  for  a  larger  cabin,  10  amperes. 
The  question  of  the  quantity  of  heat  liberated  by  the  radiators 
will  be  dealt  with  further  on. 

NON-LUMINOUS    HEATING    APPARATUS. 

In  the  other  forms  of  electric  heating  apparatus,  which  are 
very  numerous,  conductors,  or,  as  it  would  probably  be  more 


NON-LUMINOUS  HEATING  APPARATUS. 


179 


correct  to  call  many  of  them,  semi-conductors,  are  arranged 
in  various  forms,  so  that  electric  currents  can  be  delivered 
to  them,  and  so  that  the  conductors,  or  semi-conductors,  can 
deliver  their  heat  to  the  air  surrounding  the  apparatus. 

One  well-known  form  of  non-luminous  radiator,  made 
both  in  America  and  the  United  Kingdom,  is  known  as  the 
Prometheus.    It  consists  of  strips  of  mica,  upon  which  a  con- 


FIG.    24. PROMETHEUS    STATEROOM     HEATER,    ELEMENTS    AND    DETAILS. 


ductor  has  been  deposited  in  a  layer  or  film.  The  strips 
of  mica  are  provided  with  clips  at  the  ends,  in  connection  with 
the  powdered  conductor,  and  these  clips  form  the  connection 
to  the  source  of  current.  Fig.  24  shows  the  heating  elements. 
The  mica  strips  with  their  clips,  which  are  called  heating 
elements,  are  built  into  various  forms  of  apparatus,  known  as 
"convectors,"  some  of  which  are  shown  in  Figs.  25  and  26. 


180  THE    HEATING    AND    VENTILATING   OF    SHIPS. 

In  the  usual  arrangement  there  are  two  metallic  uprights, 
forming  the  connection  vto  the  supply  service,  and  the  heating 
elements  are  bridged  across  between  the  uprights,  the  whole 
being  inclosed  inside  of  some  ornamental  arrangement,  which 
may  be  cylindrical,  rectangular  or  any  other  convenient  form, 
and  which  usually  has  either  perforations  in  the  body  and  at 
the  top,  or  the   equivalent.     The  whole  apparatus   stands  a 


FIG.     25. PROMETHEUS     HEATER,     WALL     TYPE. 

little  off  the  floor,  the  air  passing  under,  up  over  the  heating 
elements,  and  out  into  the  surrounding  atmosphere. 

Another  form,  made  by  Messrs.  Isenthal,  consists  of  metallic 
resistances,  inclosed  within  a  substance  which  is  an  insulator, 
and  which  is  also  highly  refractory.  The  metallic  resistance  is 
arranged  to  have  low  coefficients,  both  of  expansion  and  of 
increase  of  resistance,  so  that  there  may  be  no  change  in  the 


NON-LUMINOUS    HEATING    APPARATUS.  181 

form  of  the  heating  elements  when  in  use.  The  heating 
elements  are  sometimes  made  with  ribs,  as  shown  in  Fig.  28, 
and  there  built  up  into  circular  or  rectangular  forms,  as  shown 
in  Figs.  29  to  32,  and  inclosed  in  various  ornamental  devices, 
the  arrangement  being  the  same  as  that  of  the  Prometheus. 
Other  firms  have  other  substances.  Messrs.  O.  C.  Hawkes, 
Ltd.,  London,  have  a  special  wire  which  they  claim  will  stand 


PROMETHEUS    HEATER,     FLOOR    TYPE. 


a  temperature  of  i,ooo°  F.  The  Simplex  Electric  Heating 
Company,  Cambridge,  Mass.,  uses  conductor  embedded  in  white 
enamel,  which  is  fused  at  high  temperature,  the  enamel  pro- 
viding the  insulation  and  also  being  very  refractory.  The 
General  Electric  Company,  Schenectady,  uses  a  high  resistance 
conductor,  coiled  into  various  forms,  and  covered  with  a 
highly-resisting  quartz  enamel.  Forms  of  these  heating  ele- 
ments are  shown  in  Fig.  33,  and  a  stateroom  heater  in  Fig.  34. 


182 


THE    HEATING    AND    VENTILATING    OF    SHIPS. 


FIG.    27. PROMETHEUS    CONVECTOR. 


Unit  with  Ribs  on 
one  side  only 


Circular  Unit  with 
Ribs. 


Unit  with  Ribs  on  Unit  with  Smooth 

each  side.  Surface 

FIG.    28. — isenthal's   heating   elements. 


HEATING    APPARATUS    WITH    LOOSE    POWDER. 


183 


NON-LUMINOUS    HEATING    APPARATUS    WITH    LOOSE    POWDER. 

There  is  another  form  of  electric  heating  apparatus,  which 
has  been  developed  in  Germany,  principally,  in  which  a  loose 
powder  is  employed,  the  necessary  resistance  being  obtained 
partly  by   means  of  the   substance  of   which   the  powder  is 


FIG.    2\). — CIRCULAR    ELECTRIC    HEATER. 


FIG.    30. BATTERY    FOR    SAME. 


composed  and  partly  by  the  fact  that  the  substance  is  in  a 
powder,  or  in  loose  grains.  A  loose  powder,  or  loose  contact 
between  any  two  conductors,  across  which  an  electric  current 
has  to  pass,  always  offers  a  considerable  resistance  over  and 
above  that  due  to  its  own  sectional  area,  length,  etc.  This  is 
the  cause  of  the  heating  of  badly  designed  switches.     If  tlie 


184 


THE    HEATING    AND    VENTILATING    OF    SHIPS. 


FIG.    31. — ISENTHAL    FLOOR-HEATING    APPARATUS. 

contact  portions  of  a  switch  do  not  make  good  contact  with 
each  other,  heat  is  always  liberated  at  the  surfaces,  and  some- 
times arcs  are  formed  with  the  attendant  enormous  heat. 

One  form  of  this  heating  appliance  is  known  as  "Kryptol." 
It  is  a  granular  mass  of  very  inoxidizable  substances,  carbon, 


FIG    32. ISENTHAL     FLOOR-HEATING    APPARATUS. 


HEATING    APPARATUS    WITH   LOOSE   POWDER. 


185 


Cartridge    Unit.  Quartz    Enamel    Unit. 

FIG.    33. GENERAL    ELECTRIC    HEATING   ELEMENTS. 

graphite,  carborundum  and  silicious  matters.  These  substances 
are  ground  together  and  then  pressed  into  blocks,  and  after- 
wards made  into  grains  of  a  uniform  size.  The  grains  for 
different  types  of  apparatus  vary  in  size  from  a  sand  to  the 
size  of  grains  of  wheat,  with  varying  amounts  of  graphite 
and  carborundum,  according  to  the  particular  applications  for 
which  they  are  required.  The  substance  is  claimed  to  stand 
temperatures  up  to  3,ooo°  F. ;  and,  on  the  other  hand,  it  is 
claimed  that  temperatures  as  low  as  500  F.  can  be  obtained. 
The  powder  or  grain  is  filled  into  cartridges,  as  shown  in 


FIG.     34. GENERAL     ELECTRIC     STATEROOM     HEATER. 


186 


THE    HEATING    AND    VENTILATING   OF    SHIPS. 


Fig.  36.  These  cartridges  consist  of  tubes  of  special  glass,  in 
which  the  resistance  material  is  held,  the  ends  of  the  tubes 
being  hermetically  sealed  with  metallic  capsules,  which  form 
the  connections  to  the  powder.  The  cartridges  are  heated  with 
an  electric  current  before  they  are  finally  closed  by  the  cap- 
sules, in  order  to  eliminate  grains  of  un-uniform  size,  and 
also  to  get  rid  of  the  moisture.    One  of  the  troubles  met  with 


FIG.    35. SALOON     ELECTRICALLY    HEATED    BY    HAWKEs'    STOVES. 


in  working  out  this  form  of  apparatus,  after  the  capsules  had 
been  fixed,  was  the  generation  of  steam  within  the  cartridge 
when  the  current  was  allowed  to  pass  through,  the  steam 
bursting  the  glass-containing  tubes.  To  meet  this  difficulty, 
any  moisture  that  may  be  present  is  driven  off  by  the  heat  of 
an  electric  current,  the  moisture  forming  steam,  and  the  heat- 
ing being  kept  up  until  this  has  all  disappeared,  and  the  whole 
mass  is  thoroughly  dry,  and  until  dry  air  is  present  between 
the  grains  of  the   substance.     The   cartridges    are   built   into 


HEATING    APPARATUS    WITH    LOOSE   POWDER. 


187 


various  forms,  and  are  arranged  as  radiators,  or  convectors, 
whichever  term  may  be  preferred,  some  of  which  are  shown 
in  Figs.  37  and  38. 

Kryptol  is  also  used,  in  certain  cases,  in  what  are  prac- 
tically open  fireplaces.  The  grains  are  loosely  heaped  in  a 
vessel  of  fireproof  clay,  the  current  being  led  to  the  mass  by 


FIG.     36. KRYPTOL     CARTRIDGES    BUILT     INTO    FRAME. 


conductors  projecting  into  them.  For  other  purposes  also  the 
Kryptol  grains  are  spread  loosely  on  a  plate  that  it  is  desired 
to  heat,  or  in  an  annular  space  surrounding  an  object  to  be 
heated,  etc. 

The  action  of  the  substance  is  as  follows:  When  the  cur- 
rent is  first  switched  on,  small  arcs  are  sometimes  formed 
between  the  individual  grains,  this  leading  to  the  very  rapid 


188 


THE    HEATING    AND    VENTILATING    OF    SHIPS. 


development  of  heat.  But  in  the  cartridge  tubes,  providing 
that  they  are  properly  prepared,  it  is  claimed  that  the  forma- 
tion of  arcs  has  been  practically  suppressed.  In  either  case, 
whether  arcs  are  formed  or  not,  the  substance  settles  down 
usually  to  a  dull  red  heat,  which  may  be  increased  up  to  the 
high  temperature  named,  if  sufficient  current  is  passed  through 
it  for  a  sufficient  time.  Where  the  substance  is  used  loose, 
practically  in  air,  the  formation  of  the  arcs  mentioned  leads  to 
the  burning  away  of  the  substance  itself  by  the  formation  of 
carbonic   oxide   and    carbonic   acid,   just   as    in   an    ordinary 


FIG.  37. 


KRYPTOL  CABIN  HEATERS. 


FIG.  38. 


furnace  or  in  an  arc  lamp.  It  is  stated,  however,  that  the 
powder  can  remain,  with  the  current  passing  through  it,  for 
several  hours  before  it  need  be  renewed. 

Some  tests  that  have  been  made  upon  a  stove  intended  for 
heating  rooms  and  containing  twenty  cartridges  inside  a  cover 
of  expanded  metal  are  interesting.  They  are  shown  by  the 
curve  in  Fig.  39.  In  the  figure  the  ordinates  are  temperatures 
in  degrees  Centigrade,  and  the  abscissae  represent  time  in 
minutes.  The  stove  was  used  to  heat  up  a  room,  whose  initial 
temperature  was  io°  C.  (50°  F.),  the  outside  temperature  being 
20  C.  (35.60  F.).     The  current  employed  was  9  amperes,  with 


HEATING    APPARATUS    WITH    LOOSE    POWDER. 


189 


a  pressure  of  120  volts — a  little  over  one  kilowatt,  or  Board 
of  Trade  unit. 

In  the  figure,  line  I.  shows  the  variation  of  the  temperature 
of  the  air  between  the  two  upper  cartridges,  with  the  cover  of 


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FIG.    39. TEMPERATURE    CURVES    OF    CARTRIDGE    STOVE. 


the  stove  removed.  The  cartridges  were  in  two  vertical  rows 
of  ten  each,  and  the  temperatures  given  would  be  between  the 
two  upper  ones,  just  inside  the  top  of  the  stove.  It  will  be 
seen  that  the  temperature  rises  in  10  minutes  from  io°  C. 
(50°  F.)  to  6o°  C.   (1400  R).     In  15  minutes  it  has  risen  to 


190  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

ioo°  C.  (2120  F.)  ;  in  20  minutes  to  1240  C.  (2550  P.).  After 
this  the  rise  is  more  gradual,  reaching  1500  C.  (3020  F.)  in 
35  minutes,  and  1520  C.  (305.60  F.),  at  which  it  remains  con- 
stant to  the  end  of  the  test,  which  occupied  an  hour.  Curve 
II.  shows  the  temperature  on  the  center  of  the  cover,  which 
was  presumably  replaced.  It  will  be  noticed  what  a  great 
difference  there  is  between  the  temperature  of  the  cover  and 
that  of  the  air  inside  of  the  apparatus  between  the  cartridges. 
The  rise  of  temperature  is  still  very  equal,  and  it  reaches  650 
C.  (1490  F.)  in  15  minutes,  but  it  reaches  88°  C.  (1900  F.) 
only  in  35  minutes,  and  does  not  rise  any  higher  to  the  end  of 
the  test.  Curve  III.  is  the  temperature  of  the  air  of  the  room 
20  millimeters  (24  inch)  above  the  top  of  the  cover.  It  will  be 
noticed  that  the  temperature  follows  the  same  course  as  that 
of  the  cover  itself,  but  is  about  40  C,  say  70  F.,  less.  Curve 
IV.  is  the  temperature  of  the  top  of  the  frame  carrying  the 
cartridges,  which,  it  will  be  seen,  follows  the  course  of  curves 
II.  and  III.  fairly  closely,  with  a  certain  difference  between 
them.  Curve  V.  is  the  temperature  of  another  portion  of  the 
cover,  not  subject  to  side  currents  of  air.  It  does  not  present 
much  interest.  Curve  VI.,  which  is  the  most  interesting  one 
of  the  whole,  is  the  temperature  of  the  room  one  meter  (39H 
inches)  above  the  cover ;  and  curve  VII.  is  the  average  tem- 
perature of  the  air  in  the  room.  It  will  be  seen  that  the  tem- 
perature of  the  air,  one  meter  above  the  cover,  and  the  aver- 
age temperature  of  the  room,  are  very  nearly  alike,  that  a 
short  distance  above  the  cover  being  slightly  higher  than  the 
average  temperature,  and  being  about  7°  C.  (12.60  F.)  above 
it  at  the  end  of  the  test.  Both  curves,  however,  rise  very 
gradually.  It  takes  25  minutes  to  increase  the  temperature 
io°  C.  (180  F.)  one  meter  above  the  stove,  and  30  minutes  for 
the  average  temperature  of  the  room  to  reach  the  same  figure. 
The  temperature  of  the  air,  one  meter  above  the  stove,  risms 
very  gradually,   it  will   be   seen,   to   about  270   C,   while   the 


HEATING   APPARATUS    WITH    LOOSE   POWDER. 


191 


average  temperature  of  the  room  rises  to  only  about  21  °  C. 

(70°  F.). 

There  is  another  instructive  series  of  curves  given  of  tests 
with  a  Kryptol  stove,  shown  in  Fig.  40.     There  are  several 


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FIG.    40. HEATING    TO   BOILING   POINT    OF    ONE    LITER   OF    WATER. 

curves,  those  on  the  left  of  the  figure  giving  the  rise  of  tem- 
perature in  the  time  shown,  with  the  Kryptol  apparatus,  and 
those  on  the  right  the  rise  of  temperature  in  the  time  shown, 
with  gas.    The  gas  employed  appears  not  to  have  been  by  any 


192  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

means  the  most  efficient  for  heating.  It  was  an  open  gas 
flame,  which  is  certainly  not  designed  for  heating.  As  will  be 
seen,  the  electrical  apparatus  takes  10  minutes  to  reach  a  tem- 
perature of  280  C.  in  the  best  of  the  three  curves  shown,  and 
over  20  minutes  to  reach  ioo°  C,  while  gas  reaches  300  C.  in 
the  worst  of  the  curves  shown  in  4  minutes,  and  ioo°  C.  in  14 
minutes. 

The  above  curves  are  taken  from  an  article  in  the  German 
Export  Zeitschrift,  dealing  with  the  subject.  The  article  also 
gives  some  other  interesting  information,  which  there  is  hardly 
space  to  reproduce  here.  Some  other  curves  are  given,  which 
show  that  the  current  required  rises  to  a  maximum,  and  then 
falls  to  a  "working"  current.  This  is  the  common  experience 
with  a  great  many  forms  of  heating  apparatus.  If  the  air  of 
a  room  is  required  to  be  heated  up  quickly,  a  considerable 
amount  of  heat  has  to  be  supplied  to  the  apparatus  for  a  short 
time,  and  then  it  may  be  reduced,  the  air  then  keeping  its  tem- 
perature with  a  smaller  expenditure. 

The  Kryptol  cartridges  described  are  made  in  the  following 
sizes:  5XA,  y%,  10,  12^4  and  20  inches  long,  by  0.6  and  0.8  inch 
diameter  respectively.  The  1224-inch  cartridge  takes  0.3 
ampere  with  a  pressure  of  100  volts,  and  the  cartridge  is 
stated  to  receive  with  that  current  and  pressure  an  increased 
temperature  of  100  degrees.  These  figures  are  for  the  cart- 
ridge when  exposed.  When  inclosed,  the  conductivity  of  the 
mixture  rises  with  the  temperature,  and  the  cartridge  will  take 
0.4  ampere  with  no  volts. 

It  will  be  understood,  as  explained  in  connection  with  hot 
water  and  steam  heating,  ".hat  the  above  remarks  apply  to 
heating,  without  having  any  regard  to  the  question  of  venti- 
lation. As  will  be  explained,  heating  and  ventilation  are 
now  usually  considered  together,  the  ventilating  air  current 
being  employed  for  heating  and  cooling  purposes.  In  many 
cases,  however,  no  attention  whatever  is  paid  to  ventilation. 


SPIRAL   COIL    HEATERS.  193 

and  this   is   particularly  the   case  with   electrical  heating  ap- 
pliances. 

It  will  be  understood  that  any  heating  appliance  may  be 
fixed  in  any  room,  passage,  alleyway,  etc.,  and  will  give  off 
heat,  exactly  in  the  proportion  described,  but  the  heat  given 
off  may  or  may  not  be  useful  heat.  In  the  case  of  corridors, 
one  very  frequently  sees  here  a  heating  appliance,  which  is 
practically  useless,  because  there  is  an  air  current  constantly 
passing  over  it,  and  constantly  carrying  off  the  heat  that  is 
liberated,  without  doing  any  useful  work.  The  same  remark 
would  apply  to  a  room  that  is  very  subject  to  drafts.  The 
heating  appliance  would  do  very  little  good.  On  the  other 
hand,  if  a  heating  appliance  is  placed  in  a  room,  say  in  the 
middle  of  a  saloon,  and  is  not  exposed  to  drafts,  it  will  heat 
up  the  air  of  the  saloon,  by  radiation  and  convection,  in  a 
certain  time,  varying  with  the  conditions,  but  the  heating  will 
be  hardly  under  the  control  of  the  engineer  in  the  same  manner 
as  it  is  when  the  appliances  are  so  arranged,  as  will  be  de- 
scribed later,  as  to  utilize  the  warmed  air  currents. 

SPIRAL  COIL   HEATERS. 

A  type  of  electric  heater  made  by  the  Consolidated  Car 
Heating  Company,  New  York,  and  fitted  for  marine  use,  is 
on  the  McElroy  spiral  coil  construction,  in  which  the  re- 
sistance coils  are  perfectly  supported  at  every  point,  rendering 
vibration  impossible.  The  spindle  supporting  the  coil  consists 
of  a  ^-inch  square  wrought  iron  rod,  on  which  are  strung 
porcelain  tubes,  so  designed  and  fitted  that  a  helical  groove 
extends  from  end  to  end.  The  iron  wire  for  the  resistance 
coil  is  wound  in  a  close  spiral  spring,  and  insulated  copper 
leading  wires  are  attached  to  both  ends  by  twisted  and  soldered 
joints.  This  coil  is  wound  between  the  ridges  on  the  porcelain 
spindle,  under  suitable  tension,  and  the  leading  wires  are 
passed   through    eccentric    bushings   at   the    ends   and    firmly 


194 


THE    HEATING    AND    VENTILATING    OF    SHIPS. 


fastened  to  the  exterior  part  of  the  circuit.  This  construction 
gives  the  greatest  possible  length  of  wire  in  the  given  space, 
and  so  disposes  every  portion  of  the  large  surface  presented 
that  a  large  quantity  of  air  comes  freely  into  contact  with  it, 


LOW    TEMPERATURE    TUBULAR    AIR    HEATER.  195 

and  passes  out  in  a  steady  stream  at  such  temperature  as  may 
be  designed. 

Two  views  of  this  type  of  heater  are  given  in  Figs.  41  and 
41  A.  The  former  is  designed  for  the  use  of  1,000  watts  (1 
kilowatt)  of  current,  measures  27  inches  in  length,  iS3A  in 
height  and  3  9/16  in  thickness.     The  "spread"  for  bolt  holes 


FIG.    4lA. SMALL    SPIRAL    COIL    HEATER    FOR    STATEROOM. 

is  7  inches,  and  the  heater,  which  contains  four  coils,  is 
finished  in  black  japan.  The  smaller  heater  shown  has  only 
two  coils,  and  measures  4%  inches  in  thickness,  with  a  spread 
of  6l/2  inches.  The  length  is  15^  inches,  while  the  oval  of  the 
case  measures  5^4  by  2>2A  inches.  The  case  is  of  heavy,  per- 
forated sheet  steel. 

LOW    TEMPERATURE    AIR    HEATER,    TUBULAR    TYPE. 

The  latest  in  air  heater  design  is  the  so-called  "low  tem- 
perature air  heater."  The  specifications  of  the  United  States 
battleship  Louisiana  called  for  electric  heaters  which  should 
have  an  operating  temperature  equivalent  to  that  of  steam 
piping.  As  a  result,  the  General  Electric  Company's  engineers 
designed  the  tubular  type  of  air  heater  shown  in  the  accom- 
panying illustration,  and  furnished  it  to  the  Louisiana.  This 
particular  type  of  heater  consists  of  three  or  more  tubular 


196  THE    HEATING    AND   VENTILATING   OF    SHIPS. 


FIG.    42. TUBULAR    TYPE,    LOW-TEMPERATURE    AIR    HEATER. 

heating  elements  inclosed  by  the  metal  "chimney"  tubes  which 
are  shown.  Each  tube  dissipates  250  watts.  The  principle  of 
this  design  is  the  combination  of  the  large  radiating  surface 
with  a  low  watt  surface  density  and  the  chimney  effect  of  the 
tube. 

It  is  manifest  that,  while  all  electric  air  heaters  may  be  said 
to  give  100  percent  efficiency,  the  practical  efficiency,  which 
is  judged  by  the  uniform  and  effective  distribution  of  the  heat 
in  the  room,  can  be  obtained  only  by  passing  a  relatively  large 
volume  of  air  over  the  heating  surfaces,  and  raising  it  only 
a  few  degrees  above  the  temperature  of  the  room.  The  oftener 
the  total  volume  of  air  in  the  room  passes  over  the  surface  of 


&* 


FIG.     43. AIR-HEATER,    CARTRIDGE    UNIT    TYPE. 


LOW   TEMPERATURE   TUBULAR   AIR    HEATER.  397 

the  heating  source,  and  the  less  temperature  difference  between 
the  outlet  and  inlet,  the  more  efficient  is  the  heating  system. 

Three  distinct  forms  of  heating  elements  are  used  by  the 
General  Electric  Company.  The  cartridge  unit  consists  of  a 
thin  tape  of  special  resistance  metal,  wound  edgewise,  insulated 
with  a  fireproof  cement  and  then  inserted  in  a  mica-lined  brass 
tube  capped  with  a  cement  plug  through  which  the  leading-in 
wires  are  brought.  The  quartz  enamel  unit  is  made  up  of  a 
resistance  wire  wound  in  a  coil  of  small  diameter,  which  is 
then  coiled  into  the  form  of  a  flat  spiral,  with  mica  insulating 
strips  between  its  convolutions,  and  held  against  a  layer  of 


FIG.     44. GENERAL     ELECTRIC     LUMINOUS    RADIATOR. 

quartz  grains  imbedded  in  enamel  on  the  bottom  of  the  heater. 
Both  of  the  foregoing  heating  units  are  practically  infusible 
and  indestructible,  but  can  be  readily  replaced  if  damaged  by 
accident.  Great  care  has  been  taken  in  the  design  of  the  heat- 
ing devices  to  insure  the  most  efficient  application  of  the  heat, 
and  at  the  same  time  to  give  proper  radiating  surface,  so  that 
nearly  all  the  apparatus  may  be  left  in  circuit  indefinitely  with- 
out fear  of  burn-out.     (See  Fig.  33.) 

The  third  form  of  heating  element  is  the  tubular  resistance, 
which  is  used  in  the  tubular  air  heater  already  described. 
This   resistance,  while  designed  only   for  comparatively  low 


198 


THE    HEATING    AND    VENTILATING    OF    SHIPS. 


temperatures,  is  one  of  the  cheapest  and  best  forms  for  air 
heaters  up  to  a  maximum  of  600  or  700  degrees  F.,  or  with  a 
density  of  2  or  2Y2  watts  per  square  inch.  It  was  first  de- 
veloped by  the  General  Electric  Company  for  rheostat  work, 
and  particularly  the  heavy  service  of  the  railway  rheostat.  It 
consists  of  a  tube  of  asbestos  wound  on  a  mandrel,  the  tube 
supporting  a  single  layer  of  resistance  wire  closely  wound,  but 
with  turns  not  touching.    The  tube  is  then  impregnated  with  a 


FIG.   46. 


PROMETHEUS      REGULATOR     DETAILS. 

fire-proof  insulating  compound,  which  gives  the  asbestos  con- 
siderable stiffness  and  forms  a  protecting  coat  over  the  re- 
sistance wire. 

REGULATING   THE  HEAT   DELIVERED  BY   ELECTRIC   HEATING 
APPARATUS. 

The  favorite  method  is  similar  to  that  described  in  con- 
nection with  the  glow  lamp  radiator.  The  heating  elements 
are  arranged  inside  the  apparatus,  in  such  a  manner  that  either 
each    element    individually,   or   groups    of    elements,    can    be 


REGULATING    ELECTRIC    HEAT.  199 

switched  in  and  out  at  will.  The  usual  arrangement  is,  for 
heating  appliances,  the  heating  elements  are  connected  in 
parallel  between  what  are  practically  two  bus-bars,  connected 
to  the  supply  service.  There  is  a  main  switch  to  disconnect 
the  whole  appliance,  and  there  are  subsidiary  switches  to 
connect  and  disconnect  either  individual  elements,  or  groups 
of  elements,  from  the  bus-bars. 

The  British  Prometheus  Company  has  another  system  of 
regulating  for  some  of  their  apparatus,  which  is  something  on 
the  lines  of  the  regulator  of  the  tramway  service.  There  is  a 
sleeve  of  approximately  square  section,  as  shown  in  Fig.  45, 
with  conductors  on  the  insides  of  the  four  faces,  connected  to 


Q 


FIG.     47. — ISENTHAL     METHOD    OF    REGULATING     WITHOUT     SWITCHES. 

the  heating  elements.  The  corresponding  fitting  (Fig.  46) 
consists  of  a  solid  piece  of  insulating  material  of  square  sec- 
tion, carrying  conductors  on  its  faces,  the  conductors  being 
connected  to  flexible  cords,  to  which  the  regulator  is  attached. 
It  is  arranged  that  the  conductors  on  the  male  portion,  when 
making  connection  with  certain  conductors  on  the  female 
portion,  allow  full,  three-quarters,  one-half  or  one-quarter  of 
the  current  strength  to  pass  as  may  be  desired,  the  arrange- 
ment being  made  by  connecting  the  different  elements  in  the 
heating  appliance  in  different  order.  Thus,  for  full  heat,  all 
the  elements  will  be  connected  in  parallel.  For  half  heat,  two 
sets  will  be  connected  in  parallel,  afterwards  being  connected 
in  series  in  each  parallel,  and  so  on,  for  the  other  heats. 


200  THE    HEATING    AND    VENTILATING   OF    SHIPS. 

Other  methods  of  varying  the  heat  include  that  shown  in  Fig. 
47,  which  is  adopted  by  Messrs.  Isenthal,  of  London,  which  is 
somewhat  similar,  though  different  in  form,  to  that  of  the 
Prometheus  Company.  The  heating  apparatus  has  three  pro- 
jecting pins  as  shown,  and  the  connecting  pipe  from  the  supply 
service  has  three  plug  holes.  When  the  three  plug  holes  are 
on  the  three  pins,  the  full  current  is  passing,  and  the  full  heat 
is  liberated.  When  the  two  plug  holes  on  the  left  engage  with 
the  two  pins  on  the  right,  the  medium  current  is  passing,  and 
when  the  two  plug  holes  on  the  right  engage  with  two  pins  on 
the  left,  a  weak  current  is  passing.  The  strengths  of  the 
currents  under  this  arrangement  are  as  one,  two  and  three. 
The  three-hole  plug  is  wired  with  twin  wire,  one  of  the  twins 
being  connected  to  the  center  plug  hole,  and  the  other  to  the 
two  outside  plug  holes. 

The  Prometheus  Company,  of  New  York,  has  a  somewhat 
similar  arrangement  for  regulating  the  heat  in  certain  cases. 
There  are  three  pins  on  the  heating  apparatus,  and  there  are 
three  terminals  on  porcelain  holders,  connected  to  three  con- 
ductors of  a  flexible  cord.  The  three  terminals  on  the  flexible 
cord  are  colored,  one  red  and  the  others  black.  By  different 
arrangements  of  the  terminals  by  engaging  the  red  terminal 
and  the  black  terminals  with  different  pins,  different  heats  are 
provided. 

THE  QUANTITY  OF  HEAT  LIBERATED  IN  ELECTRICAL  HEATING 
APPARATUS. 

Referring  to  the  formula,  H  is  given  in  watts,  when  E  is 
given  in  volts,  C  in  amperes,  and  R  in  ohms ;  these  being,  as 
marine  engineers  know,  the  units  of  electrical  power,  pressure, 
current  and  resistance.  The  watt  is  the  unit  of  power  or  the 
rate  of  doing  work,  and  it  will  be  familiar  to  engineers  from 
the  fact  that  746  watts  equal  one  horsepower.  Work  is  done 
at  the  rate  of  one  watt,  when  a  current  of  one  ampere  passes 


ELECTRICAL    HEAT    QUANTITIES.  201 

with  a  pressure  of  one  volt,  or  the  equivalent.  Thus,  in  the 
ordinary  16-candlepower  incandescent  lamp,  working  with  a 
pressure  of  ioo  volts,  and  taking  a  current  of  0.6  ampere,  the 
electrical  energy  expended  in  each  lamp  equals  100X  0-6  =  60 
watts. 

Coming  to  the  heat  question,  each  watt  liberates  0.0568 
British  thermal  unit  per  minute,  or  3.41  British  thermal  units 
per  hour.  These  figures  are  derived  from  the  figures  already 
given,  showing  that  the  heat  unit  equals  17.58  watts.  It  is 
claimed,  by  makers  of  electrical  heating  apparatus,  that  the 
whole  of  the  electrical  energy  delivered  to  the  apparatus, 
whether  it  be  in  the  form  of  the  lamps  that  have  been  de- 
scribed, or  any  one  of  the  resistance  materials  mentioned,  is 
converted  into  heat ;  and  therefore,  where  an  electrical  heating 
apparatus  is  employed  to  heat  a  room,  the  whole  of  the  elec- 
trical energy  is  applied  in  heating  the  air  and  objects  in  the 
room.  The  writer  mentions  the  claim,  and  so  far  scientists 
appear  to  have  assumed  that  the  principles  upon  which  it  is 
based  are  correct. 

It  is  assumed  by  scientists  that  every  form  of  energy,  when 
transformed  from  the  state  in  which  it  is  at  any  moment,  be- 
comes heat  sooner  or  later — that  heat  is  the  final  form  of  all 
energy,  and  that  the  heat  balance  sheet  is  the  final  court  of 
appeal  upon  all  matters  in  which  any  form  of  energy  is  con- 
cerned. It  appears  to  the  writer  that  it  is  quite  possible  that 
other  forms  of  energy  may  be  liberated,  when  electricity  is 
converted  into  something  else.  The  question  whether  this 
does  take  place,  or  not,  has  not  yet  been  examined  in  any  way 
by  scientists,  and  therefore  the  above  statement  is  given  with 
all  due  reserve,  and  the  calculations  which  follow  will  be 
understood  to  be  subject  to  that  reservation.  If  all  the  elec- 
tricity delivered  to  the  heating  apparatus  becomes  heat,  the 
calculations  are  correct.  In  any  case,  it  appears  to  the  writer 
that    any    difference    there    may   be    would   come    within    the 


202  THE    HEATING    AND    VENTILATING   OF    SHIPS. 

margin  which  every  practical  engineer  allows  himself  for  pos- 
sible sources  of  error. 

The  electric  lamps  described  above,  which  are  employed  in 
luminous  radiators,  absorb,  as  mentioned,  250  watts  each,  and 
that  would  mean  that  250  X  3-41  =  852^  British  thermal 
units  are  liberated  by  each  lamp  per  hour.  As  each  British 
thermal  unit  raises  the  temperature  of  55  cubic  feet  of  air 
1  degree  F.,  each  lamp  will  raise  the  temperature  of  47,000 
cubic  feet  of  air  1  degree  F.  in  one  hour,  or,  say,  approxi- 
mately, 4,700  cubic  feet  10  degrees  F.  in  one  hour,  two  and 
four  lamps  raising  the  temperature  of  proportional  quanti- 
ties of  air  to  the  same  degree. 

Leaving  out  for  the  moment  the  question  of  air  currents  and 
ventilation,  which  will  be  dealt  with  further  on,  it  is  a  simple 
calculation  to  find  the  number  of  lamps  required  to  raise  the 
temperature  of  a  room  of  a  given  cubical  content  through  a 
given  number  of  degrees.  The  temperature  to  which  the  air 
has  to  be  raised  varies,  of  course,  with  the  climate  and  the 
seasons,  but  taking  40  degrees  F.,  the  figure  worked  to  in  the 
calculations  which  follow,  as  the  increase  of  temperature  re- 
quired, this  would  be  provided  for  in  a  room  having  a  cubical 
content  of  1,175  cubic  feet,  by  one  of  the  lamps  mentioned,  in 
one  hour,  on  the  supposition  that  all  of  the  electricity  is  con- 
verted into  heat,  and  that  no  heat  passes  out  of  the  room 
during  the  time. 

The  above  remarks  apply  equally  to  non-luminous  radiators, 
which  are  made  to  take  various  quantities  of  electricity.  Ap- 
paratus is  made  absorbing  from  500  up  to  4,000  watts,  when 
taking  their  full  current,  and  liberating  from  1,700  to  13,600 
heat  units  per  hour.  They  are  usually  made  to  regulate  the 
current  at  one-quarter,  one-half  and  three-quarters  of  the 
full  heating  capacity,  the  heat  units  liberated  being  then  from 
425  to  3,400  with  one-quarter,  and  the  other  figures  in  pro- 
portion. 


HEATING    BY    WARMING    THE    AIR. 


203 


HEATING   BY   WARMING  THE   AIR   ENTERING   THE    ROOM. 

The  tendency  of  modern  heating  appliances,  both  on  shore 
and  afloat,  is  to  warm  each  room  individually,  each  cabin, 
saloon,  corridor,  etc.,  by  warming  the  air  entering  the  room, 


i,     |  VERTICAL 


■'  ■?     }  SECTION. 


FIG.     48. AIR-HEATING     FIRE    GRATE. 


or  a  certain  portion  of  it.  As  will  be  explained  in  dealing: 
with  ventilation,  the  latest  application  of  the  system  combines 
heating  and  ventilating.  The  ventilating  air  current  is  made 
use  of  to  warm  the  room  by  being  itself  warmed  before  it 
enters  the  room,  and  similarly  the  air  may  be  cooled  before 
entering  the  room,  and  so  keep  the  temperature  down. 


204 


THE    HEATING    AND    VENTILATING   OF    SHIPS. 


There  are  several  methods  of  warming  the  air  entering  the 
room  in  which  the  appliances  that  have  been  described  are 
made  use  of,  with  slight  modifications  that  will  be  explained, 
and  in  addition  to  these  the  whole  of  the  air  is  warmed  by 
special  apparatus,  as  described  above.  One  of  the  methods 
that  have  been  developed  on  shore  is  by  causing  a  certain  quan- 


FIG.     49. FRONT     OF     AIR-HEATING     FIRE    GRATE. 

AIR    ISSUES   THROUGH    REGISTER    AT    TOP. 


tity  of  oil  to  be  heated  by  the  stove,  or  fire  grate,  as  explained 
below,  and  to  be  delivered  into  the  room  at  a  higher  tempera- 
ture than  rules  outside. 

SPECIAL    AIR-HEATING    STOVES. 

On  shore  a  number  of  stoves  have  been  developed  that  are 
doing  very  good  work  in  hospitals  and  other  institutions,  in 
which  a  certain  quantity  of  air  is  warmed  before  it  enters  the 
room  by  being  passed  over  a  hot  surface,  specially  arranged 


SPECIAL    AIR-HEATING    STOVES.  205 

for  it,  in  the  grate  or  stove  with  which  the  room  is  heated  in 
the  ordinary  way.  The  arrangement  of  the  grate  is  shown  in 
section  in  Fig.  48,  and  a  complete  stove  is  shown  in  Fig.  49. 
This  is  the  form  made  by  George  Wright  &  Company,  Rother- 
ham. 


FIG.    50. BACK   VIEW    OF   AIR-HEATING    FIRE   GRATE. 

It  will  be  seen  that  in  place  of  the  fireplace  extending  right 
to  the  back  of  the  chimney,  there  is  a  space  behind  that  devoted 
to  the  burning  fuel  within  the  chimney  proper,  and  that  the 
hot  gases,  smoke,  etc.,  from  the  burning  fuel  are  taken  up 
through  an  iron  flue  inside  the  chimney  proper  instead  of 
being  delivered  straight  into  it  from  the  fireplace.  Air  is  led 
between  the  flue  and  the  chimney  space  from  the  outside, 
usually  by  a  duct  leading  from  the  outside  air  through  one 
of  the  outside  walls  in  the  neighborhood,  where  a  grating  is 


206 


THE    HEATING    AND    VENTILATING    OF    SHIPS. 


provided  that  can  be  arranged  to  regulate  the  quantity  of  air 
entering.  The  cold  air  from  outside  passes  through  the  duct 
over  the  hot  surface  of  the  back  of  the  fireplace  and  that  of 
the  flue  above,  and  is  delivered  into  the  room  through  gratings 
provided  for  it  at  the  level  of  the  usual  chimney  breast  in  front, 
and  sometimes  also  at  the  sides. 


FIG.     51. WARM    AIR    VENTILATING    GRATES     (GEO.    WRIGHT    &    CO.) 


In  the  large  hospital  stove  shown  in  Fig.  51  the  air  is  de- 
livered from  the  front,  sometimes  the  top,  and  always  the 
sides,  and  it  is  a  common  thing  for  hospital  wards  to  be 
warmed  by  a  stove  of  this  kind  at  the  end  farthest  from  the 
door,  and  one  or  more  pairs  of  similar  stoves  standing  back  to 
back  in  the  middle  of  the  ward,  at  a  certain  distance  from  the 
door.  Stoves  of  this  kind  are  made  for  smaller  rooms  as  well 
as  for  the  large  rooms  of  which  hospital  wards  usually  consist, 
and   it  appears    to  the   writer   that   they   could   be  very  well 


SPECIAL    AIR-HEATING    STOVES.  207 

adapted  for  heating  the  saloons,  mess  rooms,  etc.,  on  board 
ship,  the  air  to  be  warmed  being  taken  from  above  the  upper 
deck  by  a  ventilating  arrangement,  properly  protected  in  the 
usual  way,  and  brought  down  at  a  little  distance  from  the 
stove  and  then  run  in  under  the  deck  to  the  air  space  de- 
scribed. 

A  modification  of  the  air-heating  stove,  which  has  been 
used  in  a  school,  but  which  is  somewhat  crude,  consists  of  a 
stove  of  the  usual  slow-burning  type,  standing  near  the  middle 
of  the  school  room,  with  a  chimney  carried  vertically  to  within 
a  few  feet  of  the  ceiling,  and  then  carried  to  the  outer  wall  at 
an  angle  a  little  above  the  horizontal,  the  chimney  being  contin- 
ued outside  the  outer  wall  in  the  usual  way.  The  nearly  horizon- 
tal portion  of  the  flue  has  a  second  cylinder  surrounding  it,  into 
which  air  is  brought  from  outside  at  the  point  where  the  flue 
emerges,  and  the  air  is  warmed  by  its  passage  through  the 
annular  space  between  the  flue  and  the  surrounding  cylinder, 
and  is  delivered  to  the  room  above  the  stove,  warmed  to  a 
certain  temperature. 

The  arrangement  of  the  air-heating  stoves  mentioned  for 
hospitals  is  a  great  favorite  with  some  of  the  superintendents, 
because  they  say  that  the  firegrate  gives  the  ward  a  certain 
cheerfulness,  and  the  matter  of  heating  the  air  is  fully  provided 
for  by  the  arrangement  described.  The  radiation  from  the 
dancing  flames  of  the  ordinary  cheerful  fire  has  also  an  im- 
portant bearing  upon  the  subject.  The  yellow  flames  that  the 
Anglo-Saxon  so  likes  to  see  give  out  light  rays  principally; 
but,  according  to  the  latest  experiments,  the  light  rays  are  con- 
verted into  heat  rays  after  passing  through  the  skin  and  warm 
the  body,  while  the  red  rays  and  the  dark  or  invisible  heat 
rays  do  not  pass  through  the  skin,  and  have  therefore  no  useful 
effect,  unless  they  are  made  to  impinge  upon  something  that 
will  absorb  them,  such  as  the  furniture  of  the  room.  The 
hospital  superintendents  referred  to  find  that  the  ward  fires 


208  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

have  a  good  effect,  and  under  the  above  reasoning  they  are 
scientifically  correct. 

HEATING  THE   AIR   BY   MEANS    OF   STEAM,    HOT    WATER  AND 
ELECTRIC    RADIATORS. 

The  next  method  of  heating  the  air  is  by  causing  it  to  pass 
over  the  radiators  that  have  been  described,  on  its  way  into  the 
room.  It  will  be  understood  that  there  are  two  methods  of 
arranging  radiators  in  any  room  that  is  to  be  heated.  One  is 
by  fixing  the  radiator  somewhere  near  the  middle  of  the  room, 
and  allowing  the  air  of  the  room  to  be  gradually  warmed  up 
by  the  convection  currents  that  are  set  up  and  by  the  radiation 
from  the  stove.  This  method  gives  the  engineer  very  little 
control  over  the  temperature  of  the  room,  or  of  any  part  of 
the  room,  at  any  moment.  If  a  door,  for  instance,  is  left  open, 
and  the  passage  or  corridor  into  which  it  opens  contains  cold 
air,  the  heating  within  the  room  will  probably  be  very  poor, 
even  with  a  considerable  number  of  heating  appliances,  except 
in  their  immediate  neighborhood  and  on  the  opposite  side  to 
that  from  which  the  draft  is  coming.  The  case  is  very  similar 
to  that  of  the  coal  fire  with  an  open  door  or  a  very  drafty 
door. 

The  other  method  is  to  place  the  radiators,  or  other  heating 
appliances,  in  the  path  of  the  air  that  is  entering  the  room  and 
that  is  to  be  used  more  or  less  directly  for  ventilation.  Where 
ventilation  is  effected  entirely  by  windows,  by  open  door,  or, 
as  is  so  frequent,  by  loosely  fitting  doors,  it  is  practically  im- 
possible to  employ  radiators  in  this  way.  But  where  doors 
are  properly  fitted,  and  where  a  supply  of  air  is  taken  directly 
from  outside  of  the  room,  it  can  always  be  warmed  by  passing 
it  over  the  surface  of  a  radiator.  On  shore  the  usual  method 
is  to  fix  the  radiators  close  to  the  outer  walls  of  the  building; 
under  a  window  is  a  favorite  position.  Holes  are  made  in  the 
wall,  fitted  with  gratings  of  various  forms,  arranged  so  that 


HEATING   THE    AIR    BY    MEANS    OF    RADIATORS. 


209 


the  quantity  of  air  passing  through  them  can  be  regulated; 
and  the  air  entering  the  room  through  these  gratings  is  caused 
to  pass  over  the  surface  of  the  radiator  on  its  way,  and  there- 
fore attains  a  certain  temperature  before  it  mingles  with  the 
air  already  in  the  room. 

In    a    modification    of    this    arrangement,    the    radiator    is 


FIG.    52. RADIATOR    ON    SHORE    HEATING    AIR    DRAWN 

FROM    OUTSIDE.        NATIONAL    RADIATOR    COMPANY. 


specially  fitted,  as  shown  in  Fig.  52,  with  a  plate  on  the  inner 
side  of  the  radiator  tubes,  which  acts  as  a  baffle  to  the  air ;  and 
the  air  is  obliged  to  pass  over  the  full  vertical  and  horizontal 
length  of  the  radiator,  and  issues  from  it  at  a  certain  height 
above  the  floor.  It  is  given  a  certain  upward  tendency,  which 
causes  it  to  mingle  better  with  the  air  in  the  room,  and  produces 


210  THE    KEATING    AND    VENTILATING    OF    SHIPS. 

very  good  heating  effects.  The  question  of  the  exit  of  the 
air  in  these  cases  belongs  to  the  matter  of  ventilation  and 
will  be  dealt  with  fully  in  that  section.  It  may  be  mentioned 
here  that  the  vitiated  air  of  the  room  is  usually  carried  off 
by  the  chimney,  which  still  forms  a  part  of  the  equipment  of 
the  modern  house  that  is  fitted  with  radiators,  a  grate  also 
being  provided  that  can  be  used  in  case  of  emergency. 

On  board  ship,  the  equivalent  of  this  would  be  similar  to 
the  arrangement  suggested  for  the  air-heating  stoves.  Venti- 
lators bringing  air  from  the  topmost  deck,  or  from  the  outside 
atmosphere,  wherever  it  can  be  obtained  without  danger,  would 
carry  it  by  means  of  pipes  down  into  the  saloons,  cabins,  cor- 
ridors, etc.,  and  the  air  would  then  be  directed  over  the  radia- 
tors, in  the  manner  described,  and  thence  out  into  the  rooms. 
The  difficulty  involved  in  these  arrangements  is,  of  course,  that 
of  providing  the  number  of  ventilators  that  would  be  neces- 
sary, since  each  radiator  would  require  its  own  special  venti- 
lator, to  provide  its  own  supply  of  air,  though  it  might  possibly 
be  arranged  for  one  ventilator  to  supply  air  to  two  or  three 
radiators.  Unfortunately,  under  present  conditions  of  sea- 
going ships,  it  does  not  seem  practicable  to  employ  the  same 
arrangement  for  the  supply  of  air  as  is  used  on  shore,  viz., 
for  air  to  come  in  through  the  ship's  side;  though  if  valves 
can  be  arranged  that  will  allow  air  to  come  in,  and  not  water, 
when  the  ship  is  in  a  seaway,  that  portion  of  the  problem 
would  be  solved.  As  will  be  explained  in  dealing  with  venti- 
lation, something  of  the  kind  has  been  done  and  may  possibly 
be  extended. 

The  above  remarks  with  regard  to  heating  the  air,  by  pass- 
ing it  over  the  surfaces  of  radiators,  apply  equally  to  steam 
and  hot  water,  and  to  electrically  heated  radiators,  and  that,  no 
matter  whether  the  electric  heating  elements  are  of  the 
luminous  or  non-luminous  form.  In  fact,  the  majority  of 
modern    electrical    convectors    are    arranged    on    those   lines. 


HEATING    THE    AIR    BY    MEANS    OF    RADIATORS. 


211 


The  air  of  the  room  is  heated  by  passing  through  the  radiator, 
entering  it  at  the  bottom,  passing  upwards  over  the  heating 
elements,  whether  they  are  lamps  or  resistance  substances,  and 


FIG.    53. — DIAGRAM     SHOWING    ACTION    OF    STOVE    AS    AIR-HEATER. 

issues  from  the  top  of  the  apparatus  at  a  considerably  higher 
temperature.  Fig.  53,  taken  from  the  catalogue  of  Messrs. 
O.  C.  Hawkes,  Ltd.,  shows  the  idea.    The  air  issues  from  the 


212  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

top  of  the  radiator  at  a  high  temperature  and  gradually  cools 
as  it  mingles  with  the  air  of  the  room  beyond,  raising  the 
temperature  of  the  latter  air  in  the  process. 

It  may  be  mentioned  that  one  of  the  most  successful  forms 
of  gas-heated  radiators,  an  American  invention,  operates  on 
these  lines.  It  stands  out  in  the  room  in  any  convenient  po- 
sition, and  air  enters  it  from  below,  the  products  of  combustion 
and  warmed  air  issuing  from  below  a  plate  on  the  top  and 
mingling  with  the  air  of  the  room. 

AIR-HEATING    APPARATUS,    PURE    AND    SIMPLE. 

The  air  heating  apparatus,  pure  and  simple,  really  belongs 
to  the  domain  of  ventilation.  In  it  the  air  for  a  whole  build- 
ing on  shore  is  taken  hold  of,  is  cleaned  in  the  case  of  towns 
where  the  atmosphere  is  foul,  such  as  London  and  the  manu- 
facturing towns  of  the  United  Kingdom,  and  is  warmed  by 
passing  over  steam  pipes,  or  cooled  by  passing  over  pipes 
containing  either  water  or  a  solution  of  cooled  brine,  and  de- 
livered into  the  rooms  to  be  warmed  or  to  be  cooled  by  ducts 
arranged  for  the  purpose.  The  vitiated  air  is  led  away  out 
of  the  rooms  by  means  of  other  ducts,  and  is  carried  away  to 
the  outer  atmosphere. 

On  shore,  the  usual  method  is  to  build  a  shaft  on  one  side 
of  the  building,  sometimes  in  the  middle  of  the  building,  and 
carried  up  as  high  as  convenient,  and  to  a  point  where  the  air 
is  as  pure  as  it  can  be  obtained.  At  the  bottom  of  the  shaft  an 
entrance  is  made  to  the  building  by  means  of  a  large  duct 
leading  through  a  hole  in  the  wall,  and  in  this  hole  and  duct 
are  fixed  the  cleaning  arrangements  and  a  fan.  On  the  other 
side  of  the  hole,  ducts  lead  to  the  different  portions  of  the 
building,  these  ducts  branching  off  to  different  sections  of 
each  portion  of  the  building,  and  becoming  smaller  and 
smaller  as  the  cubical  space  they  have  to  supply  becomes  less. 
.    The  hole  in  the  wall  is  usually  occupied  by  the  fan,  and  the 


AIR-HEATING     APPARATUS.  213 

cleaning  apparatus  is  fixed  on  the  outside  of  the  fan,  and  also 
heating  apparatus  for  the  very  cold  winter  months.  A 
favorite  form  of  cleaning  apparatus  on  shore  is  a  kaiar  screen, 
stretched  in  front  of  the  entrance  to  the  building,  and  having 
a  stream  of  water  constantly  pouring  over  it,  the  screen  being 
further  cleaned  by  periodical  flushes  from  a  pipe  above  it, 
from  which  also  the  other  cleaning  water  proceeds. 

For  shipboard  work,  particularly  the  modern  ship  that  is 
divided  up  into  so  many  watertight  compartments,  the  prob- 
lem is  complicated  by  the  fact  that  the  deck  has  to  take  the 
place  of  the  side  of  the  building.  Any  air  that  is  taken  for 
ventilating  or  heating  purposes  must  come  from  the  deck, 
and  any  vitiated  air  that  is  expelled  must  be  carried  up  to  the 
deck.  Any  heating  or  ventilating  appliance  must  enable  the 
air  to  be  carried  separately  into  each  compartment,  and  sepa- 
rately taken  out  of  it,  back  to  the  deck.  Though  in  the  large, 
modern  liners  the  deck  is  fairly  large,  it  is  not  unlimited,  and 
the  provision  of  so  many  pieces  of  apparatus  leading  to  dif- 
ferent compartments  and  leading  from  them  is  sometimes  a 
trouble,  seeing  that  space  has  to  be  found  for  so  many  other 
things,  such  as  boats,   skylights,   winches,   etc. 

On  the  other  hand,  a  ship  at  sea  has  one  very  great  advan- 
tage over  a  building  on  shore,  especially  a  building  standing  in 
the  middle  of  a  smoky  town.  The  air  at  sea  is  as  pure  as  it  is 
possible  to  obtain,  and  therefore,  provided  that  reasonable 
care  is  taken  to  prevent  the  "stokers"  from  the  chimney  find- 
ing their  way  into  the  air  inlets,  and  to  keep  the  air  inlets 
clear  of  outlets  from  lavatories,  etc.,  any  air  inlet  arranged  on 
a  deck  that  is  open  to  the  atmosphere  must  provide  absolutely 
pure  air,  and  air  fairly  well  charged  with  ozone.  The  passage 
of  the  ship  through  the  water  also  necessarily  carries  off  the 
vitiated  air,  leaving  it  behind,  and,  providing  that  care  is  taken 
that  the  vitiated  air  outlets  are  not  placed,  with  reference  to 
the   air    inlets,    so   that    under   any   conditions   of   wind   the 


214  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

vitiated  air  can  find  its  way  fnto  the  air  inlet,  the  problem  of 
inlet  and  outlet,  subject  to  the  question  of  space,  is  a  very- 
simple  one. 

Practically  all  that  is  required  for  warming  the  air  sup- 
plying any  part  of  the  ship,  say  saloons,  staterooms,  officers' 
quarters,  etc.,  are  ducts  leading  from  inlet  apparatus  on  deck 
to  the  different  parts  of  the  ship  to  be  warmed,  and  with  a 
grid  of  steam  pipes  arranged  in  the  path  of  the  air  to  be 
warmed  (the  grid  being  provided  with  a  regulating  valve,  so 
that  the  pressure  and  temperature  of  the  steam  can  be  regu- 
lated at  will),  and  some  method  of  driving  the  air  down 
below.  Modern  practice  on  board  ship  has  settled  down  to 
the  use  of  fans,  and  they  are  used  sometimes  for  driving  the 
air  down  below,  sometimes  for  exhausting  the  vitiated  air 
from  below,  and  sometimes  for  both  purposes. 

The  following  is  an  account  of  some  work  done  by  the 
American  Blower  Company,  of  Detroit,  Mich.,  on  board  the 
ferryboats  of  the  Pennsylvania  Railroad  Company  at  New 
York.  The  air  is  heated  by  a  bank  of  steam  coils,  on  the 
lines  of  those  shown  in  Fig.  54,  which  is  fixed  in  the  hold  below 
the  main  deck.  Fresh  air  is  brought  from  above  the  main 
deck  by  means  of  a  shaft,  and  is  drawn  over  the  steam  coils 
by  means  of  a  fan  on  the  other  side  of  them,  and  when  warmed 
is  forced  through  a  system  of  galvanized  iron  ducts  into  the 
passenger  cabins,  saloons,  etc.  The  air  enters  the  cabins,  etc., 
through  openings  3  or  4  inches  in  diameter,  closed  by 
louvre  gratings,  arranged  for  controlling  the  supply  of  air  in 
the  usual  way.  Owing  to  the  limited  space,  the  ducts  were 
obliged  to  be  somewhat  small,  and  the  velocity  of  the  air  con- 
sequently rather  high.  The  heating  apparatus  was  arranged 
in  sections,  so  that  the  ducts  leading  to  the  different  parts  of 
the  ship  might  be  separately  controlled.  Other  firms  have 
arranged  apparatus  on  something  the  same  lines. 


INLETS    AND    OUTLETS    FOR   THE   AIR. 


215 


FIG.    54. AMERICAN     BLOWER    COMPANY'S    AIR-HEATER    ON     FERRY    BOAT. 


INLETS  AND  OUTLETS   FOR  THE   AIR. 

The  cowl  that  was  introduced  a  good  many  years  ago  for 
admitting  air  to  spaces  below  deck  has  been  superseded  by 
short,  vertical  pipes,  fitted  with  protecting  hoods,  the  air  pass- 
ing up  under  the  hood  and  down  the  vertical  pipe,  instead  of 
passing  into  the  mouth  of  the  cowl,  as  was  usual  in  older 
times.  The  same  arrangement  answers  equally  well  for  an 
outlet  for  the  vitiated  air.  The  principal  requirements  for 
inlets  and  outlets  are  that  they  shall  be  very  strong;  shall  be 
firmly  secured  to  the  deck;  shall  not  project  above  the  deck 
more  than  is  necessary  to  obtain  a  proper  supply  of  air;  shall 
not  be  liable  to  be  easily  carried  away  by  a  heavy  sea,  and 
shall  not  be  in  the  path  of  any  object  that  may  break  loose  in 
a  heavy  seaway.  Cases  are  on  record  in  which  the  old  form  of 
cowl  has  been  a  serious  danger  to  a  ship. 


216 


THE    HEATING    AND    VENTILATING    OF    SHIPS. 


One  in  particular  that  was  mentioned  at  a  discussion  upon 
ventilation,  at  the  Institution  of  Naval  Architects,  was  that  of 
a  ship  which  was  fitted  with  cowls,  and  which  shipped  a  very 
heavy  sea  in  a  storm,  the  sea  breaking  in  one  of  the  hatchways 
on  the  fore  deck,  and  the  ship  commencing  to  settle  by  the 


FIG.     55. TOP-SUCTION     DECK-TYPE    THERMOTANK     SUPPLYING    AIR. 


head.  The  hatchway  was  covered  in  a  comparatively  short 
time  with  tarpaulins  and  the  pumps  got  to  work,  but  it  was 
found  that  the  ship  was  still  settling  by  the  head,  and  eventu- 
ally it  was  discovered  that  the  fore  trysail  boom  had  carried 
away  one  of  the  cowls,  and  in  the  darkness  (it  was  at  4  A.  M.) 
this  had  not  been  noticed.     The  ship  had  a  well-deck,  and  the 


THE    THERMOTANK     SYSTEM. 


217 


sea  had  left  a  large   quantity  of  water  upon   it,  which   was 
finding  its  way  down  through  the  hole  left  by  the  cowl. 

THE  THERMOTANK  SYSTEM. 

An  apparatus  that  is  now  very  much  in  use  on  board  the 
leading  great  liners  and  others  is  that  developed  by  the  Ther- 


FIG.    56. TOP-SUCTION    DECK-TYPE    THERMOTANK    EXHAUSTING    AIR. 

motank  Ventilating  Company,  of  Glasgow,  in  which  the  venti- 
lating and  heating  or  cooling  arrangements  are  united  in  one, 
as  shown  in  Figs.  55  to  60.  The  apparatus  is  arranged  either 
to  force  air  down  below  under  pressure  or  to  exhaust  it,  the 
same  apparatus  being  available  for  either,  as  may  be  required. 
It  consists  of  a  tank  or  cylinder,  in  which  a  certain  number 
of  tubes  are  arranged  in  a  vertical  position,  the  air  to  be 
warmed  or  cooled  being  drawn  through  them  by  means  of  a 


218 


THE    HEATING    AND    VENTILATING    OF    SHIPS. 


fan  attached  to  and  forming  part  of  the  plant.  For  heating 
purposes,  steam  is  allowed  to  circulate  around  the  tubes,  a 
supply  being  brought  for  the  purpose  from  the  nearest  steam 
service.  For  cooling  the  air,  cold  water  or  cold  brine,  accord- 
ing to  the  lowering  of  temperature  required,  is  circulated.  In 
addition  a  steam  jet  is  arranged  to  provide  moisture  in  very- 
dry  climates. 

There  are  three  forms  of  thermotank  apparatus,  which  are 


FIG.    57. BOTTOM-SUCTION    DECK-TYPE    THERMOTANK    SUPPLYING    AIR. 


known  respectively  as  "top  suction,"  "bottom  suction"  and 
"between  decks."  The  top  suction  type,  which  is  shown  very 
clearly  in  Figs.  55  and  56,  is  taken  from  one  fixed  on  the  boat 
deck  of  the  Lusitania,  and  has  the  cylindrical  tank,  common  to 
all  of  the  apparatus,  in  which  the  pipes  are  fixed.  It  has  also 
the  mushroom  valve  that  will  be  seen  above  the  cylindrical 
tank,  and  that  is  marked  in  the  diagrams,  and  also  a  protected 
cowl  connected  to  the  fan  chamber  for  the  admission  of  fresh 
air. 


THE    THERMOTANK    SYSTEM. 


219 


When  the  apparatus  is  used  to  force  air  down  into  the  state- 
rooms, etc.,  the  mushroom  valve  on  top  of  the  tank  is  closed, 
and  the  air  passes  from  the  hooded  cowl  through  the  fan  up 
at  the  back  of  the  pipes,  down  through  the  pipes,  and  thence 
into  the  ducts  leading  to  the  rooms  to  be  warmed.  When  the 
apparatus  is  to  be  used  for  exhausting,  the  mushroom  valve 
on  top  of  the  tank  is  opened,  and  the  valves  marked  D  and  C 
at  the  base  of  the  tank  are  closed.     The  air  then,  instead  of 


FIG.    58. BOTTOM-SUCTION     DECK-TYPE    THERMOTANK    EXHAUSTING    AIR. 


being  drawn  from  the  hooded  cowl,  is  drawn  from  below,  and 
in  place  of  passing  through  the  tubes  passes  up  by  the  side  of 
them  and  through  the  mushroom  valve  at  the  top  to  the 
atmosphere.  \ 

The  bottom  suction  apparatus  is  shown  in  Figs.  57  and  58. 
It  is  very  similar  to  the  top  suction  apparatus,  the  difference 
being  the  absence  of  the  hooded  cowl  described  above.  In 
the  bottom  suction  apparatus  air  is  taken  from  below  the  fan, 


220 


THE    HEATING    AND    VENTILATING    OF    SHIPS. 


as  seen  in  the  diagram;  is  passed  through  the  fan,  and  thence 
through  the  air  tubes  and  down  into  the  ducts  leading  to  the 
rooms  to  be  warmed  or  cooled.  When  the  bottom  suction 
apparatus  is  to  be  employed  for  exhausting,  the  mushroom 
valve  above  the  tank  is  again  opened,  the  valves  C  and  D  are 
again  closed,  and  the  valve  B,  which  is  shown  in  the  diagram, 
in  the  suction  duct  leading  to  the  fan,  is  also  closed,  the  air 


FIG.    59. — 'tween  deck   type    thermotank    supplying  air. 


from  below  then  passing  up  through  the  fan,  thence  by  the 
side  of  the  air  pipes  and  out  through  the  mushroom  valve  at 
the  top. 

Figs.  59  and  6o  show  a  between-deck  apparatus.  This  is  very 
similar  to  those  described  above,  the  difference  being  that  it  is 
fixed  between  decks,  and  takes  its  air  from  a  duct  or  flue 
leading  to  any  convenient  supply  of  fresh  air.  It  is  used  either 
for  exhausting  or  forcing  air  down,  just  as  the  others  are. 


THE    THERMOTANK    SYSTEM. 


221 


In  all  forms  of  the  apparatus  there  is  a  steam  pipe  leading 
to  the  top  of  the  tank,  and  an  exhaust  steam  valve  and  steam 
trap  at  the  bottom.  A  perforated  steam  pipe,  surrounding  the 
air  tubes,  provides  the  moisture  when  required.  It  has  the 
usual  valves.  For  cooliiag,  water  or  cooled  brine,  as  ex- 
plained, take  the  place  of  steam. 

It  will  be   seen,  from  the  description,  that  the  thermotank 


FIG.   60. — 'tween  deck  type  thermotank  exhausting  air. 


apparatus  practically  does  for  the  compartments  of  a  ship 
what  the  shafts  and  fans  do  for  a  coal  mine.  The  thermotank 
apparatus  appears  also  to  have  been  more  thoroughly  worked 
out  than  the  system  of  mine  ventilation  has,  up  to  the  present. 
It  will  be  noticed  that,  providing  that  thermotank  and  ducts, 
etc.,  are  provided  for  each  compartment,  the  engineer  has 
complete  control  of  the  ventilation,  and  the  heating,  warming 
and  cooling  of  each  individual  part  of  the  ship.     It  will  be 


222  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

noticed  also  that  any  type  of  the  thermotank  apparatus  can 
be  used  either  to  force  air  into  the  spaces  to  be  warmed,  or 
cooled  and  ventilated,  or  can  be  arranged  to  exhaust  the  air 
from  them.  This  follows  the  practice  adopted  in  ships  which 
carry  cold  storage  for  fruit,  in  which  the  temperature  is  not 
required  to  be  very  low.  As  has  been  explained  under  "Cold 
Storage  on  Board  Ship,"  in  temperate  latitudes  the  "freezer" 
engineer  works  the  cold  store  upon  the  atmosphere.  That  is 
to  say,  he  merely  takes  the  air  .direct  from  the  atmosphere, 
passes  it  through  the  store  and  forces  it  out  again.  In  many 
latitudes  it  will  evidently  be  more  convenient,  and  more  eco- 
nomical, to  adopt  this  plan  with  the  ventilating  air  current 
for  shipboard  use. 

Another  point  that  should  be  mentioned  in  connection  with 
the  thermotank  apparatus,  as  will  be  seen  from  some  of  the 
illustrations,  is  that  it  is  arranged  to  regulate  the  speed  of  the 
motor,  and  with  it  the  quantity  of  air  passing  into,  or  being 
sucked  out  of,  the  spaces  operated  upon.  The  regulating  ap- 
paratus consists  simply  of  an  electrical  rheostat,  arranged  to 
vary  the  current  in  the  field  coils  of  the  electric  motor,  and 
thereby  to  vary  its  speed.  It  will  be  seen  that  this  gives  the 
engineer  a  more  complete  control  than  is  possible  with  any 
other  method,  providing  that  the  steps  of  the  regulator  can 
be  arranged  sufficiently  close  together.  As  mentioned,  how- 
ever, in  a  previous  section,  the  ventilating  air  current  increases 
very  rapidly  with  the  speed,  because  the  volume  of  air  is  in- 
creased with  the  speed,  and  the  pressure  driving  the  air  is 
also  increased.  It  is  necessary,  therefore,  that  any  regulating 
apparatus  should  be  arranged  very  finely,  so  that  the  changes 
in  the  strength  of  the  ventilating  air  current  can  be  made  very 
small  indeed,  and  the  changes  in  the  atmosphere  of  the  rooms 
under  control  made  very  gradually. 

It  is  claimed  by  the  Thermotank  Company  that  its  system  is 
very    much    more    efficient    than    any    system    of    steam-pipe 


THE    THERMOTANK    SYSTEM. 


223 


radiation,  with  exhaust  ventilation,  and  as  a  proof  of  this  claim 
are  given  the  curves  shown  in  Fig.  61,  in  which  the  time  oc- 
cupied in  heating  up  the  air  of  two  Russian  ships,  one  by  steam 
and  the  other  by  thermotank,  is  given.  In  the  figure,  the  time 
in  hours  is  plotted  on  the  base  line,  as  abscissae,  and  the  rise  of 
temperature  is  measured  by  the  vertical  distances  above  the 
base  line,  as  ordinates. 

As  will  be  seen,  with  the  thermotank,  heating  commenced 
immediately.  In  a  quarter  of  an  hour  the  temperature  had 
risen  about  n  degrees  F. ;  in  half  an  hour  it  had  risen  17 
degrees  F. ;  in  one  hour  22x/2  degrees  F. ;  and  it  continued  to 
rise  up  to  32M2  degrees  F.  at  the  end  of  four  hours.    With  the 


3o 

Sup 

pljill 

tarn 

1  Air 

«ith  J 

uenu 

o  Tan 

L. 

M 

M 

P, 

M 

STRi 

IMA 

1! 

;■■ 

n 

Opt 

Mta 

u  l-i  | 

a  Radiation 

»-iib 

r.u,„ 

ist  V 

nlilation  1 

.  8.  8 

HOi 

KVA 

I 

ower 

■)«llt 

. 



—  ■[—- 

—  - 

-"- 

lain  Deck 

b 

--^= 

^ 

r 

H       H       $i       I  8       Time  in  Uuurs.      3  4  5 

FIG.    61. — THERMOTANK    HEATING    COMPARED    WITH    OPEN    STEAM    PIPES. 

steam-pipe  heating,  the  temperature  rises  only  about  I  de- 
gree in  a  quarter  of  an  hour;  2  degrees  in  half  an  hour; 
5  degrees  in  one  hour  and  two-thirds  on  the  lower  deck,  and 
a  little  over  two  hours  on  the  main  deck;  the  total  rise  in 
five  hours  being  only  9  degrees  on  the  lower  deck,  and  about 
8  degrees  on  the  main  deck. 

These  results  are  very  striking,  but  though  every  credit 
should  be  given  to  the  Thermotank  Company  for  the  way  in 
which  the  apparatus  has  been  worked  out,  the  test  in  ques- 
tion by  no  means  shows  that  an  equal  result  might  not  have 
been  obtained  by  the  aid  of  steam,  or  by  electricity,  if  the 
steam  or  electrical  heating  apparatus  had  been  as  suitably  and 
carefully  arranged  as  the  thermotank  apparatus  was. 


224 


THE    HEATING    AND    VENTILATING    OF    SHIPS. 


In  these  tests,  the  Kostroma  was  fitted  with  a  thermotank 
supplying  fresh  air  into  a  compartment  of  14,803  cubic  feet  in 
extent.  The  heating  surface  was  208  square  feet.  There  were 
246  persons  in  the  compartment,  the  air  of  which  was  changed 
6.9  times  per  hour.  There  were  7  cubic  feet  of  air  supplied 
per  person  per  minute. 


FIG.     62. TOP-SUCTION     DECK-TYPE    THERMOTANK     FOR    FIRST     CLASS 

ACCOMMODATION     ON    LUSITANIA. 


The  Moskva  had  open  steam  pipe  radiation,  with  exhaust 
ventilation.  On  the  main  deck,  the  compartment  in  question 
had  a  volume  of  20,309  cubic  feet,  contained  262  persons,  and 
was  fitted  with  202  square  feet  of  heating  surface.  The  air 
was  changed  seven  times  per  hour,  thus  giving  each  person  9 
cubic  feet  of  fresh  air  per  minute.     On  the  lower   deck,  a 


THERMOTANKS    ON    THE   LUSITANIA. 


225 


compartment  of  20,930  cubic  feet  was  heated  by  a  surface  of 
191  square  feet.  There  were  284  persons,  supplied  each  with 
1 1  cubic  feet  of  air  per  minute,  the  air  being  changed  eight  and 
three-quarter  times  per  hour. 


FIG.    63. BOTTOM-SUCTION    DECK-TYPE  THERMOTANK    FOR    FIRST 

CLASS    ACCOMMODATION    ON     LUSITANIA. 


THE   APPLICATION    OF  THE  THERMOTANK   TO    THE   STEAMSHIP 
LUSITANIA. 

It  will  perhaps  be  interesting  to  describe  the  application  of 
the  thermotank  system  to  one  of  the  latest  of  the  large  ocean 
liners.  The  whole  of  the  heating  and  ventilating  of  the  Lusi- 
tania  and  Mauretania  is  practically  carried  out  by  thermotanks. 
These  are  arranged,  a  large  number  of  them  on  the  boat  deck, 
and  a  small  portion  between  decks.  They  deliver  through 
ducts  leading  to  all  the  spaces  to  be  warmed  and  ventilated, 
and  through  louvre  valves  into  each  compartment,  the  valves 


226  THE    HEATING    AND    VENTILATING   OF    SHIPS. 

being  fixed  near  the  ceiling.  The  warmed  air  passes  in  at  the 
higher  level,  and  is  carried  out  by  means  of  other  valves 
near  the  deck,  into  the  alleyways,  etc.,  from  which  it  is  car- 
ried off  to  the  atmosphere.  In  warm  weather,  when  cooling 
is  required,  the  direction  of  the  air  current  is  reversed  by 
altering  the  arrangement  of  the  valves  in  the  thermotank  ap- 
paratus, as  explained,  and  the  air  is  exhausted  from  the  dif- 
ferent compartments  through  the  louvre  valves,  into  the  ducts, 
and  thence  through  the  thermotanks  to  the  atmosphere. 

That  portion  of  the  ship  allotted  to  first  class  passengers 
has  twenty-four  thermotanks,  principally  fixed  on  the  boat 
deck,  around  the  funnels,  and  they  draw  air  principally  from 
gratings  opening  on  to  the  promenade  deck  shelter,  so  as  to 
avoid  drawing  in  .air  that  is  exhausting  from  the  galleys,  etc., 
on  to  the  boat  deck.  When  the  thermotanks  are  exhausting, 
the  air,  of  course,  passes  away,  and  the  question  of  the  odors 
from  galleys,  etc.,  does  not  arise.  It  appears  to  the  writer  that 
a  certain  amount  of  the  injector  action  that  has  been  men- 
tioned will  take  place  in  the  thermotank  apparatus,  when  it  is 
being  used  to  exhaust,  though  the  action  will  be  reduced  by 
the  special  arrangement  of  the  protecting  cowl  shown. 

The  space  devoted  to  second  class  passengers  has  nine  ther- 
motanks ;  the  third  class,  eleven  thermotanks ;  and  the  officers 
and  crew,  five;  the  thermotanks  being  arranged  on  the  tops 
of  deck  houses  and  where  convenient.  Those  in  the  fore  end 
of  the  ship  are  placed  between  decks,  and  fresh  air  is  ob- 
tained for  them  from  the  upper  deck  abaft  the  navigating 
bridge,  so  that,  it  is  claimed,  a  supply  of  fresh  air  is  ob- 
tained in  the  worst  weather  without  the  exposure  of  cowl 
heads,  etc.,  in  the  forward  part  of  the  ship. 

The  thermotanks  are  stated  to  be  capable  of  changing  the 
air  in  the  different  compartments  up  to  eight  times  per  hour, 
and  of  maintaining  a  temperature  of  65  degrees  F.  in  the 
coldest  weather;   The  system  of  thermotanks  is  inter-connected, 


THERMOTANKS    ON    THE    LUS1TANIA. 


227 


so  that  in  case  of  the  breakdown  of  any  individual  apparatus 
a  supply  can  be  obtained  from  one  of  the  others. 

The  arrangement  of  inter-connection  appears  to  the  writer 
to  be  a  very  good  one,  though  it  necessarily  somewhat  compli- 
cates the  apparatus.    The  large  number  of  thermotanks  that  it 


~-  J     . 

[#»  '     / 

"Tj!^- 

R-5SS5S55 

- 

1      \ 

* 

**     JmY' 

;  ..  /,'.'■-.■ 

KIG.     64. BOTTOM-SUCTION     DECK-TYPE     THERMOTANK     FOR    SECOND 

CLASS    ACCOMMODATION    ON    LUSITANIA. 

is  necessary  to  employ  (forty-nine  in  all)  is  also  a  matter  for 
consideration,  as  it  takes  up  a  great  deal  of  space  on  the  boat 
deck  and  elsewhere,  and  it  adds  to  the  apparatus  to  look  after. 
On  the  other  hand,  the  engineering  staff  of  a  large  liner  is 
thoroughly  qualified  to  look  after  the  apparatus,  and,  in  fact 


228  THE    HEATING    AND   VENTILATING   OF    SHIPS. 

their  labors,  with  ordinary  care,  should  not  be  greatly  in- 
creased by  the  employment  of  the  apparatus. 

In  the  Lusitania,  in  addition  to  the  thermotanks,  twelve 
powerful  exhaust  fans  are  connected  by  trunks  to  all  the 
galleys,  pantries,  bathrooms,  lavatories,  etc.,  the  fans  being 
of  sufficient  capacity  to  change  the  air  at  least  fifteen  times 
an  hour.  The  holds  and  other  compartments,  forward  and  aft, 
are  also  mechanically  ventilated,  so  that  the  provision  men- 
tioned above  of  the  air  from  the  compartments  finding  its  way 
to  the  alleyways,  etc.,  and  thence  to  the  atmosphere,  is  easily 
arranged,  and  the  whole  system  of  ventilation  and  of  heating 
and  cooling  the  different  compartments  of  the  ship  appears  to 
be  exceedingly  well  provided  for. 

One  serious  objection  arises  from  the  fact  that  it  has  been 
necessary  frequently  to  supply  both  inside  and  outside  state- 
rooms from  the  same  thermotank.  The  heat  generated  in  the 
interior  of  these  ships  by  the  immense  boiler  plants,  and  dissi- 
pated and  radiated,  to  a  large  degree,  by  both  the  main  tur- 
bines and  the  numerous  auxiliary  engines,  keeps  the  inside  of 
the  ship  at  a  relatively  high  temperature ;  with  the  result  that 
of  two  rooms,  side  by  side,  one  being  against  the  side  of  the 
ship  and  the  other  inside,  there  will  be,  particularly  in  winter 
weather,  a  difference  of  temperature  amounting  in  some  cases 
to  as  much  as  10  degrees  F.,  and  occasionally  much  more.  If, 
now,  the  same  heat  be  supplied  to  each,  the  inner  room  will 
become  insufferably  hot  before  the  outer  gets  comfortable.  In 
such  a  case  as  this  some  auxiliary  method  of  regulation  be- 
comes well-nigh  imperative ;  and  it  is  reported  that  this  will  be 
supplied  by  fitting  small  electric  heaters  to  the  outside  rooms, 
and  allowing  these  to  make  up  any  difference  necessary  be- 
tween a  comfortable  temperature  in  the  inside  rooms  and  the 
corresponding  temperature  in  those  next  the  skin  of  the  ship. 
Automatic  regulation  of  these  heaters  will  be  provided,  so  as 
to  minimize  the  consumption  of  current  and  conduce  to  the 
largest  comfort  of  the  passenger. 


VENTILATION. 


229 


FIG.    65. 


'TWEEN    DECK    TYPE    THERMOTANK    FOR    THIRD    CLASS    ACCOMMODA- 
TION   ON    LUSITANIA. 


VENTILATION. 


In  the  preceding  sections,  as  explained,  the  writer  has  dealt 
with  heating  alone,  but  he  has  mentioned,  from  time  to  time, 
that  heating  and  ventilating  are  very  closely  allied,  that  you 
cannot  warm  any  room,  for  instance,  or  have  any  source  of 


230  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

heat  present  in  any  room,  without  producing  air  current.^ 
which  necessarily  ventilate  to  a  greater  or  less  extent.  He 
now  proposes  to  discuss  the  question  of  ventilation  by  itself, 
having  already  shown  how  the  two  can  be  worked  together. 

Ventilation,  as  explained  in  the  opening  article  of  this  series, 
is  to  the  atmosphere  of  any  room,  or  any  space  in  which  men 
have  to  work  or  live,  what  water  is  to  dirt.  Atmospheric  air 
has  the  property  of  carrying  off  noxious  gases,  such'  as  the 
carbonic  acid  gas  that  is  given  off  at  each  breath  by  the  lungs 
of  men  and  animals,  the  exhalations  that  are  constantly  being 
given  off  from  the  skin  of  everyone,  the  microbes,  bacilli,  and 
even  the  dust  that  is  always  present.  If  a  continuous  current 
of  air  is  provided,  passing  through  living  rooms,  etc.,  the 
whole  of  these  should  be  carried  harmlessly  away. 

In  addition  to  the  above,  atmospheric  air  has  the  property 
of  absorbing  the  vapor  of  water,  and  can  therefore  be  em- 
ployed in  cooling  by  evaporating  moisture,  such  as  the  perspira- 
tion on  our  skins,  and  also  can  be  employed  to  deliver  the 
necessary  moisture  to  the  atmosphere  of  a  room  when  it  has 
become  dry  from  other  causes.  As  is  well  known,  for  com- 
fort, we  require  that  a  certain  quantity  of  moisture  shall  be 
present  in  the  air  we  breathe.  If  less  than  that  quantity  is 
present  we  experience  a  sense  of  discomfort.  Our  tongues 
and  the  insides  of  our  mouths  feel  dry.  On  the  other  hand,  if 
the  air  has  too  much  moisture  we  experience  another  kind  of 
unpleasant  feeling.  We  cannot  keep  cool.  The  perspiration 
does  not  evaporate,  and  therefore  does  not  fulfil  its  natural 
function. 

It  will  be  seen,  therefore,  that  the  provision  of  a  supply  of 
fresh  air  constantly  passing  through  living  rooms,  etc.,  is 
necessary  for  health.  On  shore  the  test  of  pure  air  is  taken  to 
be  the  presence  of  a  minimum  percentage  of  carbonic  acid  gas. 
Sea  air,  which  is  taken  to  be  the  purest  form  of  air,  contains 
about  three  volumes  of  carbonic  acid  gas  in  10,000  volumes  of 


VENTILATION.  231 

air.  The  limit  taken  on  shore,  by  educational  authorities  and 
others,  is  from  eight  to  ten  volumes  of  carbonic  acid  in  every 
10,000  volumes  of  air. 

According  to  the  latest  view  of  scientists,  carbonic  acid  gas 
has  been  made  more  or  less  of  a  bogey.  From  tests  that  have 
been  made  it  has  been  shown  that  human  beings  can  live, 
without  inconvenience,  in  an  atmosphere  containing  a  very 
much  higher  percentage  of  carbonic  acid  than  that  given 
above.  On  the  other  hand,  however,  it  appears  to  be  quite 
correct  in  the  majority  of  cases  to  take  the  percentage  of 
carbonic  acid  present  in  the  atmosphere,  which  can  be  tested, 
as  a  guide  for  the  purity  of  the  atmosphere,  with  reference  to 
the  other  matters,  organic  impurities,  etc.,  that  have  been 
mentioned  above.  But  this  is  not  always  strictly  correct.  In 
the  case,  for  instance,  of  lavatories,  the  carbonic  acid  present 
may  be  comparatively  small,  while  the  organic  matters,  as 
evidenced  by  the  smell,  may  be  comparatively  large.  The 
special  case  of  lavatories  is  dealt  with  later  on. 

Ventilation  is  known  as  natural  or  mechanical,  according  to 
whether  it  is  left  to  take  care  of  itself  or  is  more  or  less  con- 
trolled. Mechanical  ventilation  is  also  sometimes  known  as 
either  "plenum"  or  "vacuum."  Marine  engineers  have  exactly 
the  same  division  in  the  matter  of  their  furnace  draft,  natural 
ventilation  corresponding  roughly  to  natural  draft  and  me- 
chanical ventilation  to  forced  or  induced  draft.  Plenum  venti- 
lation, which  has  already  been  described  when  dealing  with 
methods  of  heating  air,  corresponds  to  forced  draft  and 
vacuum  ventilation  to  induced  draft.  Natural  ventilation  can 
perhaps  hardly  be  said  to  correspond  to  chimney  draft.  It  cor- 
responds really  to  a  condition  that  would  be  present  if  there 
were  no  chimney. 

Perhaps  the  different  methods  of  ventilation,  and  the  princi- 
ples of  ventilation  itself,  will  be  best  understood  by  a  refer- 
ence to  the  case  where  it  is  of  the  greatest  importance,  viz. : 


232  THE    HEATING    AND   VENTILATING    OF    SHIPS. 

in  coal  mining.  In  a  number  of  coal  mines,  it  will  be  remem- 
bered, as  the  coal  is  removed  from  its  bed,  gases  are  given 
off,  which,  if  mixed  with  air  in  certain  proportions,  will  ex- 
plode and  do  great  damage  if  a  light  is  presented  to  them. 
The  explosive  mixture  is  between  5  and  15  percent  of  the 
gas  in  the  atmosphere  of  the  mine.  When  the  gas  is  present 
in  a  greater  quantity  than  15  percent  it  will  not  explode, 
because  it  cannot  contain  sufficient  oxygen  for  combination. 
On  the  other  hand,  when  the  quantity  present  is  less  than  5 
percent  it  will  not  explode,  because  it  is  too  much  diluted  with 
the  nitrogen  of  the  atmosphere.  These  figures  apply  also  to 
dangers  from  the  vapor  of  petrohum  in  tank  ships.  In  the 
United  Kingdom,  therefore,  successive  acts  of  Parliament 
have  decreed  that  a  certain  volume  of  air  shall  be  passed 
through  all  coal  mine  workings,  the  volume  being  sufficient 
to  very  quickly  dilute,  below  the  explosion  point,  any  gas 
which  comes  away.  Probably  this  illustrates,  as  well  as  any- 
thing, the  cleansing  action  of  atmospheric  air. 

The  majority  of  mines  in  the  United  Kingdom,  and  a  large 
number  in  the  United  States,  lie  wholly  below  ground,  and 
are  reached  by  two  vertical  shafts,  one  of  which  conveys  fresh 
air  to  the  mine  and  the  other  carries  off  the  vitiated  air  from 
the  workings.  From  the  two  shafts,  which  are  named  re- 
spectively "down  cast"  and  "up  cast,"  two  main  roads  run  into 
the  mine,  called  respectively  the  "in-take,"  which  extends 
from  the  down  cast,  and  which  carries  the  fresh  air  into  the 
workings,  and  the  "return,"  which  carries  the  vitiated  air  from 
the  workings  to  the  up  cast.  Roadways,  or  air  passages,  con- 
nect the  two  main  roads  in  such  a  manner  that  there  is  a  con- 
stant current  of  air  passing  across  all  working  faces  from 
the  in-take  to  the  return. 

In  the  early  days  of  coal  mining,  what  would  now  be  termed 
natural  ventilation  ruled.  The  air  current  was  left  to 
take    care    of    itself.      Usually    the    warm,    moist,    vitiated 


VENTILATION.  233 

atmosphere  from  the  workings  found  its  way  to  one  of  the 
shafts,  and  being  lighter  than  the  column  of  air  in  the  other 
shaft  a  certain  difference  of  air  pressure  was  set  up  between 
the  two,  which  caused  a  certain  variable  and  uncertain  circu- 
lation of  air  through  the  workings.  It  was  no  uncommon 
thing  in  those  days  for  the  direction  of  the  ventilating  air  cur- 
rent to  be  reversed.  In  those  days  also,  occasionally,  there 
was  only  one  shaft.  It  was  sometimes  divided  by  brattice 
cloth  into  two,  the  vitiated  air  rinding  its  way  up  one  half  and 
the  fresh  air  moving  down  the  other  half.  In  some  cases 
even  this  division  was  not  provided,  and  the  air  in  those  cases 
formed  a  division  of  its  own,  the  warmed  air  escaping  up  one 
side  of  the  shaft  while  the  cold  air  passed  down  the  other 
side.  The  state  of  the  coal  mines  in  those  days  illustrates  very 
forcibly  what  natural  ventilation  really  means.  Practically 
there  was  very  little  ventilation  at  all.  Any  change  in  the  tem- 
perature of  the  atmosphere  outside  might  stop  the  course  of 
the  ventilating  current  entirely. 

The  first  improvement  was  the  provision  of  a  furnace  in 
the  neighborhood  of  the  bottom  of  the  up-cast  shaft,  which, 
by  providing  a  column  of  hot  air  in  that  shaft,  created 
what  mining  engineers  call  a  motive  column,  by  means  of 
which  the  air  from  the  outside  atmosphere  passed  down  the 
down-cast  shaft  and  through  the  workings  to  the  up-cast. 
In  most  modern  coal  mines  the  furnace  has  given  way  to 
the  fan,  which  is  usually  placed  at  the  top  of  the  up-cast  pit. 
It  is  placed  there  principally  because  the  up-cast  pit  was  cov- 
ered in  when  furnace  ventilation  ruled,  to  prevent  the  ingress 
of  the  colder  air  to  the  shaft,  thereby  neutralizing  the  effect 
of  the  furnace,  and  it  was  simpler  to  make  use  of  the  existing 
arrangements  and  to  adopt  the  fan  to  them  than  to  make  new 
arrangements.  In  a  few  cases,  however,  the  fan  is  fixed  at 
the  top  of  the  down-cast  shaft,  and  forces  air  into  the  mine, 
the  vitiated  air,  as  before,  finding  its  way  out  through  the 


234  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

up-cast  shaft.  In  a  few  cases,  also,  the  fan  at  the  top  of  the 
pit  is  assisted  by  fans  at  the  level  of  some  of  the  seams  that 
are  worked  from  the  pit,  and  also  by  fans  placed  in  different 
positions  in  the  workings,  to  direct  the  currents  of  air  over 
particular  portions  of  the  working  faces,  etc. 

Marine  engineers  will  recognize  a  practical  counterpart  to 
their  own  arrangement  for  supplying  their  boiler  furnaces 
with  air.  Furnace  ventilation  of  a  mine  corresponds  to  the 
ordinary  chimney  draft  of  a  boiler,  and  fan  ventilation  cor- 
responds to  forced  or  induced  draft,  according  to  whether  a 
pressure  or  exhaust  fan  is  employed. 

The  writer  would  call  attention  to  one  very  striking  feature 
in  connection  with  mine  ventilation,  which  he  thinks  will 
assist  marine  engineers  to  follow  the  work  that  has  been 
done  in  the  ventilation  of  buildings,  ships,  etc.  It  will  be 
noticed  that  the  shafts,  the  roads,  together  with  a  fan  or 
furnace,  form  a  complete  circuit,  corresponding  exactly  to  an 
electric  circuit.  The  shafts  and  the  main  roads  correspond 
to  the  main  distributing  cables  of  a  two-wire  electrical  supply 
service.  The  branch  roads,  connecting  the  working  faces 
with  the  main  roads,  correspond  to  the  branch  cables  or  wires 
connecting  lamps  or  motors  to  the  main  supply  cables.  The 
furnace,  where  one  is  employed,  corresponds  to  a  battery, 
where  one  is  used  to  supply  current,  and  the  fan  corresponds 
to  an  electric  generator. 

The  correspondence  is  even  closer  than  this.  Just  as  suc- 
cessive coils  of  wire,  passing  through  the  magnetic  field  of  a 
dynamo  machine,  produce  successive  increments  of  electrical 
pressure,  so  the  passage  of  the  successive  blades  of  a  fan 
produce  successive  increments  of  air  pressure.  Further,  air 
encounters  resistance  in  its  passage  through  a  mine,  just  as  an 
electric  current  encounters  resistance  in  its  passage  through 
a  conductor,  and  the  resistance  in  both  cases  varies  directly 
as  the  length  and  inversely  as  the  sectional  area.     Thus,  the 


VENTILATION.  235 

greater  the  length  of  the  main  roads  of  a  mine  through  which 
the  air  current  has  to  pass,  the  greater  is  the  resistance  offered 
to  its  passage,  and  the  greater  must  be  the  air  pressure, 
measured  in  water  gage,  to  overcome  it.  Also,  the  larger 
the  air  passages  the  less  is  the  resistance  offered. 

The  latter  statement  will  appear  at  first  sight  to  be  incorrect, 
inasmuch  as  the  resistance  to  the  passage  of  air  through  any 
roadway,  pipe  or  duct  depends  directly  upon  the  friction  of 
the  air  against  the  sides  of  the  duct,  roadway,  etc.,  and  evi- 
dently the  larger  surface  of  the  larger  road  will  create  more 
friction  than  a  smaller  surface  of  a  smaller  road.  But  there  is 
another  factor  in  the  problem  in  connection  with  air.  The 
resistance  offered  to  its  passage  varies  as  the  square  of  its 
velocity,  and  its  velocity  increases  with  a  given  air  delivery 
as  the  area  of  the  road  or  duct  through  which  it  passes  is 
reduced ;  and,  therefore,  though  the  increase  of  the  size  of  the 
road  or  duct  increases  the  friction  offered  by  the  surface,  the 
total  resistance  is  considerably  lessened,  because  the  velocity 
is  also  lessened.     . 

And  all  this  applies  to  the  ventilation  of  buildings,  of  ships, 
etc.  Modern  ships  in  particular  correspond  in  a  great  many 
respects  to  the  modern  coal  mine  in  the  matter  of  ventilation. 
The  modern  ship  is  divided  into  compartments  by  athwartship 
bulkheads,  and  in  the  case  of  very  large  ships  like  the 
Lusitania  by  fore-and-aft  bulkheads.  It  thus  becomes  neces- 
sary to  deal  with  each  compartment,  from  the  topmost  deck, 
downwards,  by  itself.  In  the  Lusitania  two  compartments 
that  are  abreast  sometimes  communicate  by  watertight  doors, 
as  in  the  case  of  the  electrical  engine  room,  and  while  the 
doors  are  open  they  can  be  dealt  with  as  one ;  but  the  separate 
compartments  as  a  rule  have  to  be  dealt  with  separately,  and, 
just  as  with  a  coal  mine,  all  the  fresh  air  has  to  be  brought 
from  the  surface,  in  this  case  the  deck,  and  the  vitiated  air 
must  be  carried  off,  either  on  the  same  deck  or  at  some  point 


23G  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

where  it  will  not  mingle  with  the  air  that  is  going  down  below. 

The  ventilation  of  ships  has  gone  through  very  much  the 
same  course  of  development  as  the  ventilation  of  mines.  In 
the  early  days  it  was  left  to  take  care  of  itself,  open  hatches 
and  open  ports  being  trusted  to  do  the  work.  Later  on  the 
equivalent  of  furnace  ventilation  was  established,  ducts  being 
led  into  the  holds,  mess  rooms,  saloons,  etc.,  the  other  ends  of 
the  ducts  being  carried  to  the  neighborhood  of  the  funnel,  and 
the  circulation  of  the  air  being  set  up  by  the  heated  column 
of  air  produced  by  the  hot  gases  in  the  funnel,  fresh  air 
being  allowed  to  enter  by  cowl.:  ,and  other  arrangements  pro- 
vided for  them. 

In  the  early  days  of  heating  and  ventilating  of  ships  com- 
pressed air  was  used  in  some  cases  to  provide  suction  of  the 
air  out  of  the  hold  and  between  decks  on  the  well-known  in- 
jector principle,  fresh  air  being  allowed  to  find  its  way  down 
below  by  air  inlets  something  on  the  lines  of  the  cowls  that 
have  been  mentioned ;  but  all  these  systems  have  given  way  to 
the  use  of  the  fan,  since  electricity  has  been  established  on 
board  ship  and  the  convenience  of  the  electrically-driven  fan 
has  been  appreciated. 

Another  point  of  importance  should  be  noted  here.  It  is 
absolutely  necessary  that  there  shall  be  a  complete  circuit 
wherever  ventilation  is  to  be  carried  on.  In  the  case  of  the 
coal  mine,  the  circuit  is  from  the  atmosphere,  say  at  the 
entrance  to  the  down-cast  shaft,  through  the  down-cast  shaft, 
the  in-take  airway,  the  branch  roads,  the  return  airway,  the 
up-cast  shaft  to  the  atmosphere  again.  In  the  case  of  the  air 
supply  of  a  boiler  furnace,  it  will  be  remembered,  there  is  the 
same  circuit.  From  the  atmosphere,  by  various  passages  to 
the  stoke  hole,  through  the  ashpit,  the  fire  bars,  the  fuel,  the 
fire  tubes,  the  up-take  and  the  funnel  to  the  atmosphere  again. 
Just  as  with  an  electric  circuit,  if  the  circuit  is  broken,  or  if 
the  passage   of   the   current   is   cut  off,  the   working   of   the 


VENTILATION.  237 

apparatus  the  current  operates  is  also  stopped ;  so  if  the  venti- 
lating circuit  is  broken  at  any  point,  if  the  passage  of  the  air 
current  is  cut  off  by  any  obstruction,  the  working  of  the  venti- 
lating air  current  is  also  stopped.  Further,  just  as  with  an 
electric  circuit,  if  a  resistance  is  introduced  into  the  path  of  the 
current  the  strength  of  the  current  itself  is  reduced  with  any 
given  pressure,  so  if  any  obstruction  is  introduced  into  the 
path  of  the  air  current,  whether  for  ventilation  or  for  a  boiler 
furnace,  the  strength  of  the  air  current,  with  any  given  air 
pressure,  is  reduced. 

It  was  mentioned  above  that  the  resistance  offered  to  the  air 
current  depends  directly  upon  the  length  of  the  path  through 
which  the  air  has  to  move,  and  inversely  as  the  sectional  area 
of  the  path.  In  other  words,  the  smaller  the  duct  through 
which  the  air  supply  is  carried  the  greater  is  the  resistance 
offered  to  its  passage,  and  this  means  that  the  greater  is  the 
pressure  which  has  to  be  employed  in  delivering  the  air  cur- 
rent, and  the  greater  the  velocity  of  the  air  current  itself. 
In  this  matter  the  ventilation  of  ships  is  at  a  disadvantage 
compared  with  the  ventilation  of  buildings  on  shore  and  with 
that  of  mines,  though  the  advantage  is  not  often  taken  full 
advantage  of  on  shore. 

For  perfect  ventilation,  and  for  the  avoidance  of  what  is 
known  as  a  draft,  the  air  should  circulate  with  a  very  low 
velocity,  from  3  to  5  feet  per  second,  but  in  order  to  do  this 
the  ducts  through  which  it  circulates  must  be  large,  and  on 
board  ship,  even  in  the  very  largest  liners,  it  is  not  possible 
to  allow  a  sufficient  space ;  as  usual,  a  compromise  has  to  be 
effected.  The  ducts  have  to  be  made  as  large  as  the  other 
requirements  of  the  ship  will  allow,  their  length  as  short  as 
can  be  conveniently  arranged,  and  the  requisite  current  of  air 
must  be  made  up  by  increasing  the  velocity  as  required. 

A  striking  instance  of  what  may  be  done  by  the  provision 
of  large  ducts  will  probably  make  the  matter  clear.     At  the 


238  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

Birmingham  General  Hospital,  where  the  plenum  system  has 
been  carried  out  very  carefully  under  the  direction  of  an 
able  architect,  it  is  not  possible  to  feel  any  draft  anywhere. 
The  whole  of  the  building  is  subject  to  a  very  gentle  air 
current,  and  as  one  passes  from  corridor  to  ward,  or  ward 
to  corridor,  one  is  absolutely  unconscious  of  any  change. 
Those  who  have  visited  the  usual  run  of  hospitals,  where  the 
windows  are  kept  wide  open  on  the  stairs,  while  the  wards 
are  kept  warm  in  winter,  will  have  sometimes  a  painful  ex- 
perience of  the  great  change  in  the  temperature  between  a 
ward  and  the  landing  outside. 

Further,  at  this  hospital,  the  smells  that  are  so  often  in 
evidence,  such  as  those  of  dinner,  of  medicines,  etc.,  are  abso- 
lutely unknown.  Everyone  will  be  familiar  with  the  un- 
pleasant smell  there  always  is  about  a  restaurant  immediately 
after  dinner,  and  usually  also  in  the  neighborhood  of  the 
wards  of  a  hospital  while  dinner  is  going  on  and  immediately 
afterwards.  One  can  frequently  tell,  a  little  way  off,  if  cab- 
bage is  an  article  of  diet,  and  so  on.  At  the  Birmingham 
General  Hospital  there  is  no  sign  of  anything  of  the  kind. 
The  ventilating  air  current  carries  off  all  odors,  just  as  the 
ventilating  current  of  a  coal  mine  carries  off  the  explosive 
gases.  And  this  effect  is  produced  with  the  expenditure  of  a 
very  small  amount  of  power — 20  horsepower  only — and  with 
an  air  pressure  of  only  1/20-inch  water  gage.  Marine  engi- 
neers hardly  need  reminding  how  very  small  a  pressure  this  is. 

At  Birmingham  the  result  is  produced  by  very  large  ducts. 
In  the  main  duct  a  dozen  men  can  stand  abreast,  and  there  is 
almost  head  room  for  a  man  to  stand  on  another  man's 
shoulders  to  reach  the  ceiling.  The  branch  ducts  are  in  pro- 
portion, and  the  result  is  as  described.  As  against  this  the 
ventilating  air  current  of  the  majority  of  coal  mines,  though 
the  airways  in  the  best  of  them  are  wide  and  high,  is  very 
powerful    indeed,   and   it   is   a   serious   source   of   danger   to 


VENTILATION.  239 

working  miners  coming  from  the  coal  face,  where,  in  spite 
of  the  air  current,  the  temperature  in  deep  mines  is  very 
high  indeed,  and  where  their  physical  exertion  causes  profuse 
perspiration,  for  them  to  come  out  into  the  cold  air  current 
of  the  main  roads. 

As  explained  above,  it  is  not  possible  to  provide  large  ducts, 
even  in  the  largest  ships,  for  ventilating  air  currents ;  but,  on 
the  other  hand,  the  lengths  of  the  ducts,  even  those  leading  to 
the  lower  decks,  is  not  great. 

As  mentioned  above,  the  ventilation  of  ships  has  settled 
down  to  the  motion  of  the  air  by  fans  just  as  has  the  ventila- 
tion of  coal  mines,  and  just  as  the  tendency  of  modern  boiler 
work  is  to  provide  either  forced  or  induced  draft  by  the  aid 
of  fans.  As  with  coal  mines,  also,  and  as  with  boiler  furnaces, 
the  air  may  be  forced  into  the  space  to  be  ventilated  by  a 
pressure  fan,  the  vitiated  air  being  allowed  to  escape  by  any 
convenient  outlet,  or  the  air  may  be  exhausted  from  the  space 
to  be  ventilated  by  a  suction  fan,  and  fresh  air  drawn  into 
the  space  through  any  convenient  inlet.  The  one  thing  to 
remember  in  all  cases  where  efficient  ventilation  is  sought  is 
that  there  must  be  an  inlet  and  an  outlet,  and  that  the  same 
quantity  of  air  which  passes  in  must  pass  out. 

A  point  that  should  be  noted  here  is  that  where  the  space 
to  be  ventilated  is  also  heated,  whether  the  air  is  heated 
artificially  on  its  way  to  the  space,  or  whether  it  is  heated 
in  the  space,  either  artificially  or  by  the  presence  of  men  or 
animals  in  the  space,  the  volume  of  air  passing  out  will 
usually  be  greater  than  that  passing  in,  and  therefore  the 
outlets  should  have  a  larger  area  than  the  inlets.  The  prob- 
lem in  this  case  is  the  same  as  that  in  connection  with  both 
mine  ventilation  and  the  supply  of  air  to  a  furnace.  The  fan 
supplying  induced  draft,  it  will  be  remembered,  must  be 
larger,  in  the  sense  that  it  will  allow  a  larger  volume  to  pass 
through  it  than  the  fan  required  for  forced  draft,  because  the 


240  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

volume  of  the  hot  gases  is  larger  than  the  volume  of  the  air 
that  is  to  be  delivered  to  the  fan.  In  the  case  of  the  ventila- 
tion of  saloons,  cabins,  etc.,  the  difference  in  volume  of  the 
air  will  usually  not  be  great,  but  the  caution  given  above 
should  be  remembered,  in  order  that  those  who  are  responsible 
for  the  designing  of  systems  of  ventilation  for  ship-board 
work  should  be  careful  not  to  make  the  outlets  smaller  than 
the  inlets.  Making  either  an  inlet  or  an  outlet  small  throttles 
the  passage  of  the  air  through  it,  increases  the  pressure  at 
which  the  air  has  to  be  driven  through  the  space  to  be  venti- 
lated, and  increases  the  tendency  to  drafts. 

For  ventilation,  therefore,  whether  of  the  between  decks 
where  cattle  are  carried,  the  large  living  spaces  where  steerage 
passengers  are  carried,  or  the  saloons,  staterooms,  or  officers' 
cabins,  the  same  principle  holds  good.  Air  must  be  brought 
from  the  deck  to  the  space  to  be  ventilated,  and  the  vitiated 
air  must  be  allowed  to  find  its  way  back  to  the  deck  or  to  the 
outside  of  the  ship.  In  some  of  the  White  Star  liners  air  is 
brought  down  from  the  deck  under  pressure,  is  directed 
through  ducts  into  the  staterooms,  and  is  allowed  to  escape 
through  the  ports  of  the  staterooms,  saloons,  etc.,  when  the 
ports  are  open,  and  when  the  ports  are  not  open  the  air 
escapes  by  a  duct  provided  specially  for  it,  opening  into  the 
the  ship  on  the  inside,  and  opening  into  the  atmosphere  on  the 
outside  of  the  ship,  but  protected  by  a  valve  on  the  outside, 
which  is  open  when  the  sea  does  not  rise  to  it,  but  which 
closes  automatically  when  the  ship  rolls  and  dips  that  end  of 
the  duct  or  if  the  sea  washes  up  to  it.  The  writer  understands 
that  this  method  is  giving  way  to  the  system  that  has  been 
worked  out  by  the  Thermotank  Company,  in  which  all  air  is 
taken  from  the  deck  and  returned  to  the  deck. 

In  the  case  of  cabins,  staterooms,  etc.,  opening  to  the  atmos- 
phere, such  as  those  on  the  upper  decks,  boat  decks,  etc.,  where 
there  are  any,  the  system  of  ventilation  can  be  modified.    Air 


VENTILATION    AND    HEATING    AND    COOLING.  241 

may  be  taken  in  or  expelled  from  the  side  of  the  cabin,  but 
provision  must  be  made  for  the  exit  of  the  air.  In  the 
Lusitania,  in  some  of  the  cabins  on  the  upper  deck,  an  ad- 
justable inlet  is  provided  for  the  air  in  the  side  of  the  cabin, 
and  it  is  exhausted  by  a  duct  leading  to  the  boat  deck,  a  small 
electrically-driven  fan  providing  motive  power  for  the  air 
when  required. 

In  some  of  the  cabins  on  the  boat  deck  of  one  of  the  White 
Star  liners  the  writer  noticed  another  ingenious  method  of 
ventilation,  based  upon  the  injector  principle.  A  T-shaped 
pipe  was  fixed  on  the  side  of  the  cabin,  the  central  portion,  the 
stem  of  the  T,  projecting  into  the  cabin,  and  the  top,  or  cross, 
of  the  T  being  arranged  fore  and  aft  outside  of  the  cabin. 
As  the  ship  goes  through  the  water  air  rushes  through  the 
portion  of  the  pipe  outside  of  the  cabin,  and  draws  air  through 
the  connecting  piece  leading  to  the  cabin,  causing  a  current  of 
air  to  pass  out  of  the  cabin,  through  the  after  portion  of  the 
fore-and-aft  piece.  This  would  probably  make  a  very  efficient 
ventilating  arrangement,  but  it  must  again  be  remembered 
that  some  method  of  providing  the  inlet  air  must  be  arranged 
or  the  ventilation  cannot  go  on.  The  inlet  air  may  be  pro- 
vided by  a  protected  duct  leading  to  the  deck  above,  or  in 
any  other  convenient  way. 

VENTILATION    AND    HEATING   AND    COOLING. 

The  connection  between  heating  and  ventilating  has  already 
been  explained,  and  that  between  cooling  and  ventilating  to  a 
certain  extent.  It  will  be  understood,  from  what  has  been 
said,  that  once  possession  is  obtained  of  a  current  of  air 
passing  continuously  through  a  room,  a  saloon,  mess  room, 
cabin,  etc.,  it  can  be  employed  for  warming  the  room,  cooling 
it,  providing  it  with  moisture,  or  reducing  the  moisture  pres- 
ent by  merely  placing  the  heating,  cooling,  humidifying  or 
drying    apparatus    in    the    path   of    the    air    current,    and    by 


242  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

properly  proportioning  the  heat  supplied,  the  heat  extracted, 
or  the  moisture  supplied  or  extracted,  to  the  requirements  of 
those  occupying  the  room.  Also,  it  will  be  understood  that, 
with  properly  arranged  apparatus,  it  should  be  possible  to 
vary  the  heating,  cooling  or  moisture  at  will  in  each  compart- 
ment dealt  with. 

VENTILATION    OF    LAVATORIES    AND    CATTLE    SPACFS 

The  ventilation  of  lavatories  and  between  the  decks  where 
cattle  are  carried  presents  some  difficult  problems.  So  far  as 
the  writer  is  aware  the  between  decks  for  cattle  have  not  been 
subject  to  any  special  method  of  ventilation,  but  lavatories 
have,  and  in  his  opinion  the  between  decks  for  cattle,  and 
even  in  some  cases  the  steerage  quarters,  might  with  advantage 
be  subject  to  the  apparatus  to  be  described.  The  difficulty  in 
the  matter  of  ventilation  in  these  cases  is  the  effluvia  that  is 
too  often  present,  and  that  even  a  powerful  ventilating  cur- 
rent sometimes  fails  to  get  rid  of. 

The  remedy  appears  to  be  the  addition  of  ozone-making 
apparatus  to  the  ordinary  ventilating  current.  Ozone,  it  will 
be  remembered,  is  oxidized  oxygen.  Its  chemical  symbol  is 
03;  oxygen  in  the  ordinary  way  usually  combining  only  as  02. 
Ozone  is  the  great  vivifying  agent  that  is  so  much  sought 
after  by  invalids  who  take  sea  passages  and  who  go  to  the 
seaside.  It  has  a  very  peculiar  and  by  no  means  a  pleasant 
odor.  It  may  be  smelt,  especially  in  the  early  morning,  on 
open  hill  sides,  and  on  the  decks  of  ships  at  sea,  and  again  at 
the  seaside,  in  particular,  close  down  to  the  water's  edge. 

It  is  oxygen  in  a  very  powerful  condition,  and  its  office  is  to 
oxidize,  that  is  to  say,  to  burn  up  the  microbes,  bacilli,  etc., 
which  produce  the  offensive  effluvia  and  which  will  cause  dis- 
ease if  allowed  to  remain.  Ozone  is  produced  by  elec- 
tricity. It  may  always  be  smelt  by  those  who  know  its 
characteristic    odor    after    a    thunder    storm.     It    is   created 


VENTILATION   OF   LAVATORIES   AND   CATTLE    SPACES.  243 

in  fairly  considerable  quantities  by  every  flash  of  lightning, 
and  by  the  silent  discharges  which  take  place  during 
thunder  storms  which  do  not  give  rise  to  lightning.  It  is 
created  industrially  by  the  aid  of  high-tension  alternating  cur- 
rents, combined  with  what  are  called  electrical  condensers. 
The  electrical  condenser  is  quite  different   from  the  steam 


FIG.    66.— SIMPLEX    OZONE    PRODUCER,     EXTERNAL    VIEW. 

condenser.  Every  electric  cable  is  an  electrical  condenser. 
Whenever  two  conductors  are  close  together,  but  separated  by 
an  insulator,  an  electrical  condenser  is  formed  by  them,  and 
if  an  electric  current  is  delivered  to  one  conductor  a  charge 
of  electricity  is  delivered  to  and  absorbed  by  the  insulating 
substance  separating  the  two  conductors. 
For     ozone-making     apparatus     condensers     are     formed 


244  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

sometimes  of  glass  tubes  with  conductors  arranged  inside  and 
out,  and  sometimes  of  glass  plates,  with  sheets  of  metal  foil 
between.  In  the  Anderson  apparatus,  which  is  illustrated  in 
Figs.  66  and  67,  the  condenser  consists  of  the  glass  tubes 
shown,  with  conductors  in  the  form  of  coils  of  wire  on  the 
outside  and  other  conductors  on  the  inside.  In  all  electrical 
condensers  one  of  the  conductors  is  connected  to  earth,  in 
this  case  to  the  body  of  the  ship,  and  a  high-tension  alternating 
current  is  delivered  to  the  other  conductor.  The  condenser  is 
arranged  to  be  placed  in  the  path  of  an  air  current,  and  the 
constant  charge  and  discharge  of  the  electrical  condenser, 
produced  by  the  passage  of  the  alternating  current,  converts 
ozone  into  the  oxygen  of  tHe  air  passing  through  it,  the  ozon- 
ized air  being  then  delivered  wherever  it  is  required. 

The  high-tension  current  is  produced  on  shore  by  the  alter- 
nating currents  of  the  ordinary  town  supply  service,  raised  to 
very  high  tension — several  thousand  volts — by  means  of 
stationary  transformers,  similar  to  those  that  are  used  for 
the  distribution  of  high-tension  currents.  Up  to  the  present,  so 
far  as  the  writer  is  aware,  alternating  currents  have  not  been 
employed  on  board  ship,  and  therefore  some  arrangement  is 
necessary  for  converting  the  continuous  currents  to  alter- 
nating. This  may  be  done  by  means  of  small  motor  genera- 
tors, consisting  of  two  distinct  machines,  a  continuous-current 
motor  taking  current  from  the  lighting  or  power  service  of 
the  ship,  and  an  alternating-current  generator,  whose  armature 
is  driven  by  the  electric  motor.  The  alternating  current  can 
be  transformed  by  a  stationary  transformer  to  the  high  pres- 
sure necessary. 

Another  method  which  has  been  adopted  by  Mr.  Anderson 
in  his  apparatus,  and  which  it  is  claimed  answers  the  purpose, 
is  to  employ  the  continuous  current  taken  from  the  lighting 
or  power  service  of  the  ship  and  to  subject  it  to  very  rapid 
interruption,  very  much  on  the  lines  of  a  trembler  bell  or  the 


VENTILATION   OF   LAVATORIES    AND   CATTLE    SPACES. 


245 


induction  coil  employed  with  motor  cars.  A  special  form  of 
Interrupter  is  used  and  a  charge  and  discharge  of  the  electrical 
condenser  is  obtained,  this  giving  rise  to  the  ozone  required, 


FIG.    67.— SIMPLEX   OZONE   PRODUCER,    AS   SUPPLIED   TO   WHITE   STAR   STEAMERS 
BY   THOMAS   ANDERSON. 


which  is  directed  where  it  is  wanted.  In  use  the  ozone  gen- 
erator must  be  placed  in  the  path  of  the  air  current  that  is  to 
circulate  through  the  lavatory  or  other  space  to  be  dealt  with, 
the  ozonized  air  being  allowed  to  circulate  through  the  space, 


246  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

and  the  resultant  air  being  carried  off  by  a  separate  duct  in  the 
usual  way. 

FANS    USED   IN    VENTILATING. 

There  are  two  distinct  classes  of  fans  that  are  employed 
in  ventilation,  known  as  the  "propeller"  and  the  "centrifugal" 
fan.  Their  names  practically  explain  them.  The  propeller 
fan  is  really  a  screw,  constructed  on  the  lines  of  the  screw 
propeller  of  a  steamship,  and  it  screws  air  just  as  the  pro- 
peller of  a  steamship  screws  .water.  It  will  be  remembered 
that  with  any  screw  moving  in  any  medium  one  of  three 
things  must  move;  the  screw  itself  may  move  on,  as  where  the 
ordinary  wood  or  metal  screw  is  moved  into  a  piece  of  wood 
or  metal;  the  object  to  which  the  screw  is  attached  may  move 
forwards,  as  in  the  case  of  many  mechanical  appliances,  and, 
in  particular,  in  the  case  of  the  steamship,  which  moves 
through  the  water  as  the  screw  drives  it ;  thirdly,  if  the  screw 
and  the  object  to  which  it  is  attached  are  both  fixed,  the 
taiedium  in  which  the  screw  turns  must  move,  and  this  is  what 
takes  place  with  the  propeller  fan.  As  the  fan  turns  it  screws 
a  portion  of  the  air  from  one  side  of  it  to  the  other,  just  as 
the  propeller  of  a  steamship  screws  astern  a  portion  of  the 
water  in  which  it  is  moving.  But  with  air  propellers  the  air 
<*nly  moves.  Fans  of  this  kind  are  available  only  for  moving 
quantities  of  air  under  very  low  pressure.  They  do  not 
create  any  appreciable  water  gage  and  cannot  work  against  a 
resistance.  If  the  air  in  front  of  them  or  behind  them  is 
throttled  they  produce  practically  no  motion  in  the  air.  They 
are  of  great  service  for  directing  air  from  the  outside  of  a 
cabin  to  the  inside,  or  from  the  inside  of  a  cabin  to  the  out- 
side, and  for  that  purpose  they  should  be  fixed  in  the  bulk- 
head of  the  cabin,  or  overhead  in  the  beams  of  the  cabin  if 
preferred.  Their  office  is  simply  to  transfer  the  air,  at  a  given 
rate,  from  the  one  side  of  the  bulkhead  or  the  beams  to  the 
other  side.     Fans  of  this  type  are  often  use4  to  stir  up  the 


FANS    USED    IN    VENTILATING. 


247 


air  inside  of  living  rooms,  saloons,  etc.,  and  they  undoubtedly 
do  stir  up  the  air,  but  it  can  hardly  be  said  that,  when  used 
in  that  way,  they  produce  ventilation  in  the  proper  sense  of 
the  term.  Churning  up  the  air  in  a  room  may  tend  to  assist 
ventilation  to  a  small  extent,  but  it  can  hardly  be  said  to  pro- 
duce ventilation  itself. 


FIG.     68.— STURIEVANT     KAN     DRIVEN     BY     ELECTRIC     MOTOR. 

The  centrifugal  fan  works  on  the  same  principle  as  the 
centrifugal  pump.  In  its  simplest  form  it  consists  of  a  num- 
ber of  blades,  arranged  radially  around  a  central  space  and 
fixed  between  two  disks.  As  the  blades  are  revolved  the  air 
in  the  spaces  between  them  is  driven  outwards  by  centrifugal 
force,    a   difference   of    pressure   being   created    between    the 


248  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

central  space  and  the  periphery  of  the  fan.  This  causes  air 
to  enter  the  central  space,  and  the  air  that  has  been  forced 
outwards  to  be  delivered  from  the  periphery  at  a  certain 
velocity.  Numerous  patents  for  the  construction  of  centri- 
fugal fans  are  in  existence,  all  designed  to  increase  their 
efficiency.  The  simple  fan  described  above  is  not  efficient, 
because  the  air  between  adjacent  blades  is  not  simply  forced 
outwards.  A  portion  of  it  is  forced  outwards,  but  other 
portions  form  eddies  between  the  blades,  the  eddies  absorbing 


FIG.    G9.— STURTEVANT    FAN. 

power   from  whatever  is  driving  the   fan,  and  reducing  the 
quantity  of  air  usefully  delivered. 

The  various  forms  of  fans  are  principally  on  the  lines  of 
curvature  of  the  blades,  somewhat  similar  to  the  curvature  of 
the  blades  of  centrifugal  pumps,  the  object  being  to  eliminate 
the  eddies  formed  in  the  air  between  the  blades,  to  direct  the 
air  into  the  spaces  between  the  blades,  and  again  to  direct  it 
out  at  the  periphery  of  the  fan,  with  sufficient  energy  to  per- 
form the  work  it  is  intended  for,  but  with  no  surplus  energy. 
With  centrifugal   fans  practically  any  pressure  that  may  be 


FANS    USED    IN    VENTILATING.  249 

required  can  be  obtained.  It  is  not  necessary  to  mention  to 
marine  engineers  that  air  pressure  is  measured  by  inches  of 
water  gage,  but  it  may  be  mentioned  that  with  modern  centri- 
fugal fans  pressures  as  high  as  io-inch  water  gage  have  been 
obtained,  and  greater  pressures  could  be  produced  if  re- 
quired. On  the  other  hand,  for  ventilating  purposes,  the 
pressure  should  be  kept  as  low  as  possible.    As  mentioned,  at 


FIG.    70.— SIROCCO    FAN. 

the  Birmingham  General  Hospital  the  pressure  at  the  fan  is 
only  1/20-inch  water  gage,  but  in  the  great  majority  of  cases 
pressures  from  1  inch  and  upwards  are  employed. 

Fig.  68  shows  one  of  the  Sturtevant  Company's*  plate  fans, 
constructed  for  pressure  or  exhaust.  Another  type  of  the 
same  make  is  shown  in  Fig.  69.  In  Fig.  70  is  shown  a  fan 
built  by  the  Sirocco  Engineering  Company,  New  York. 

*  Hyde  Park,  Mass. 


250  THE    HEATING    AND   VENTILATING    OF    SHIPS. 

SIZES  OF  FANS    REQUIRED. 

The  size  of  the  fans  required  for  driving  air  through  spaces 
to  be  ventilated  depends  upon  two  quantities :  the  volume  of 
air  to  be  delivered  per  minute  and  the  velocity  or,  what 
amounts  to  the  same  thing,  the  pressure  at  which  it  is  de- 
livered. The  problem  is  very  similar  to  that  of  the  chimney 
for  the  boiler  furnace,  and  to  that  of  the  fans  employed  for 
furnishing  forced  or  induced  draft.  It  will  be  remembered 
that  the  sectional  area  of  the  chimney  must  be  large  enough 
to  accommodate  the  quantity  of  hot  gases  that  may  have  to 
pass  through  it  when  the  boilers  are  doing  their  hardest  work, 
and  it  must  also  be  high  enough  to  give  the  requisite  motive 
column  to  drive  the  air  and  gases  through  the  furnace,  flues, 
etc.  Similarly,  with  forced  and  induced  draft  the  fans  must 
be  large  enough  to  allow  of  the  passage  of  the  air  or  hot  gases 
through  them  without  throttling,  and  must  be  able  to  produce 
the  necessary  pressure  to  drive  them. 

With  ventilating  the  same  thing  occurs.  The  fans  employed 
must  be  large  enough  to  allow  of  the  passage  through  them 
of  the  largest  quantity  of  air  that  may  be  required,  and  they 
must  be  able  to  furnish  the  pressure  necessary  to  drive  that 
quantity  of  air  through  the  ventilating  system. 

With  the  propeller  fan,  the  size  of  the  fan,  that  which  rules 
the  quantity  of  air  it  can  pass,  is  its  diameter,  and  the  pressure 
obtained  from  it  depends  upon  its  speed.  The  pressure  ob- 
tainable with  any  propeller  fan  is  very  small,  and  in  practice 
on  board  ship  only  very  small  fans  are  employed,  driven 
usually  by  small  electric  motors,  and  capable  of  handling  the 
ventilation  of  cabins,  small  mess  rooms,  or  of  assisting,  or 
as  electrical  engineers  would  say,  "boosting,"  the  ordinary 
ventilating  current  in  saloons,  etc.  There  is  a  point  that  may 
be  mentioned  in  connection  with  propeller  fans,  though  it  will 
hardly  come  into  the  practice  of  heating  and  ventilating  on 


THE  POWER  REQUIRED  BY  THE  FAN.  251 

board  ship.  As  explained,  the  propeller  blades  carry  the  air 
from  one  side  of  the  fan  to  the  other  as  they  move,  just  as 
the  propeller  of  a  steamship  carries  the  water  from  one  side 
of  it  to  the  other,  but  while  this  is  true  of  the  outer  portions 
of  the  blades  of  the  propeller,  there  is  a  return  air  current  at 
the  center  of  the  propeller,  which  may  be  seen  by  testing  with 
a  ribbon,  or  something  of  that  kind.  This  return  current, 
which  is  in  the  nature  of  an  eddy,  very  much  on  the  lines  of 
the  eddies  that  seamen  are  familiar  with  in  rivers  and  on  the 
coast,  necessarily  lessens  the  efficiency  of  the  fan,  and  re- 
quires more  power  to  be  employed  in  driving  it. 

With  centrifugal  fans,  the  size,  in  the  sense  of  the  ability 
to  accommodate  volumes  of  air,  the  size  which  corresponds  to 
the  sectional  area  of  the  chimney,  is  the  width  of  the  fan,  the 
width  between  the  disks  which  usually  inclose  the  blades.  The 
wider  the  fan  the  larger  the  quantity  of  air  it  will  accommo- 
date without  thrcttling.  It  will  be  understood  that  the  air 
passages  in  a  fan  offer  resistance  to  the  passage  of  the  air 
through  them,  just  as  the  passages  through  which  steam 
passes  in  doing  work  offer  resistance  to  its  passage,  and  that 
this  resistance  makes  a  charge  upon  the  power  that  must  be 
delivered  to  the  fan  shaft  by  the  electric  motor,  or  whatever 
is  driving  it.  Thus  a  small  fan  may  require  a  larger  power 
than  would  be  necessary  to  do  the  same  amount  of  work  in 
moving  the  air  by  a  larger  fan. 

The  pressure  delivered  by  the  fan  varies  with  the  square  of 
its  speed.  It  is  not  possible  to  give  any  rule  for  the  size  of 
fan  required  for  any  given  work  nor  the  speed,  because  there 
are  so  many  fans  upon  the  market,  every  one  of  which  differs 
in  the  pressure  it  furnishes  per  revolution  and  in  the  capacity 
for  allowing  the  passage  of  air. 

THE  POWER  REQUIRED  BY  THE  FAN. 

As  marine  engineers  know,  power  is  required  to  move  the 


252  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

air  under  any  given  conditions,  and.it  depends  directly  upon 
the  quantity  of  air  to  be  moved  and  on  the  velocity  at  which 
it  is  moved.  Air  has  weight,  and  creates  friction  when  moving 
through  pipes,  ducts,  etc.  Both  of  these  features  demand  the 
expenditure  of  energy  when  the  air  has  to  be  moved.  The 
matter  may  be  put  in  another  way — the  power  required  de- 
pends upon  the  velocity  at  which  the  air  is  moved  and  the 
pressure  that  is  required  to  move  it.  In  the  case  of  a  com- 
plete ventilating  circuit,  from  the  entrance  of  a  duct  leading 
to  a  room  to  be  ventilated,  to  the  exit  from  the  duct  leading 
back  to  the  atmosphere,  the  power  required  will  be  measured 
by  the  velocity  at  which  the  air  is  moved,  multiplied  by  the 
difference  of  pressure  between  the  inlet  of  the  fan  and  the 
exhaust  of  the  system.  The  pressure  would  be  measured,  of 
course,  outside  of  the  fan  or  other  apparatus  employed  to 
move  the  air. 

It  will  be  noticed  that  the  conditions  are  exactly  the  same 
as  in  the  case  of  an  electric  circuit.  It  will  be  remembered 
that  the  power  required  in  an  electric  circuit  is  measured  by 
the  current  passing  in  the  circuit,  multiplied  by  the  pressure 
required  to  drive  the  current  through  the  circuit. 

In  the  case  of  air,  the  whole  of  the  pressure  employed  in 
the  air  circuit  must  be  taken  into  the  calculation  for  finding 
the  power  required.  Thus,  if  the  air  is  moving  under  a  pres- 
sure of  2-inch  water  gage,  and  the  duct  has  an  area  of  12 
square  inches,  the  total  pressure  will  be  24-inch  water  gage, 
or  a  total  of  13  ounces;  i-inch  water  gage,  it  will  be  remem- 
bered, being  equal  to  0.55  ounce  on  the  square  inch.  When 
the  total  pressure  and  velocity  are  known  the  horsepower  in 
the  air  is  given  by  the  formula 

p  X  v 

H.  P.    = , 

33,000 
where  p  is  the  pressure  in  pounds  per  square  inch  and  v  it* 


TESTING   THE   AIR   CURRENT.  253 

the  velocity  in  feet  per  minute.  This,  however,  is  the  horse- 
power in  the  air  only,  and  takes  no  account  of  the  efficiency 
of  the  fan  or  other  losses ;  and  in  estimating  the  actual  horse- 
power required,  when  the  quantities  given  above  are  known, 
it  will  be  wise  to  double  the  figures  obtained  from  the  last 
formula. 

It  was  mentioned  above  that  the  pressure  created  by  a 
centrifugal  fan  varies  as  the  square  of  the  speed.  The  power 
absorbed  by  the  fan  varies  as  the  cube  of  the  speed.  When 
the  speed  of  a  fan  is  increased  two  operations  take  place : 
the  quantity  of  air  delivered  by  the  fan  is  increased,  and  the 
pressure  at  which  the  air  is  delivered  is  also  increased,  and 
hence  the  cube  ratio  for  the  power.  When  a  fan  is  running, 
each  blade,  as  it  goes  around,  delivers  a  certain  quantity  of 
air  to  the  duct,  or  whatever  it  may  be  delivering  into,  and 
the  greater  number  of  revolutions  the  fan  makes  the  greater 
is  the  quantity  of  air  delivered  and  in  exactly  the  same  pro- 
portion. The  velocity  of  the  air  issuing  from  the  fan  neces- 
sarily varies  as  the  square  of  the  speed  of  the  fan  in  accord- 
ance with  the  well-known  laws. 

TESTING    THE    AIR    CURRENT. 

In  any  system  of  ventilation,  or  of  combined  heating  and 
ventilating,  it  is  necessary  to  test  the  course  of  the  ventilating 
current  and  also  the  velocity.  The  course  of  the  ventilating 
current  can  be  traced  with  comparative  ease  by  the  use  of 
light  pieces  of  ribbon  held  on  the  end  of  a  stick  in  the  air 
current.  The  paper  windmills  that  are  made  for  children 
to  play  with  are  also  very  useful  for  the  purpose,  as,  if 
properly  made,  they  are  very  sensitive.  They  must  be  placed, 
it  will  be  remembered,  with  their  axes  facing  the  direction  of 
the  wind,  and  they  will  be  found  to  show  the  direction  and 
a  rough  approximation  of  the  force  of  the  wind  very  readily. 

To  estimate  the  velocity  of  the  air  current  an  anemometer 


254  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

must  be  employed.  It  is  an  instrument  which  requires  a  con- 
siderable amount  of  skill  in  handling.  It  consists  of  a  short 
brass  cylinder,  carrying  what  is  virtually  a  small  propeller  fan 
pivoted  on  an  axis  in  the  center  of  the  cylinder,  and  arranged 
to  count  up  its  revolutions  on  one  of  the  usual  dials.  The 
apparatus  must  be  placed  so  that  the  fan  blades  receive  the 
air  current  in  the  same  manner  as  an  air  current  would  be 
created  by  a  propeller  fan,  and  the  test  is  made  by  counting 
the  number  of  revolutions  in  a  given  time. 

MEASURING  THE  AIR  PRESSURE. 

The  simplest  method  of  measuring  the  air  pressure  is  by 
means  of  the  apparatus  with  which  marine  engineers  will  be 
familiar — the  water  gage — consisting  of  a  U-tube,  having 
water  in  the  bend  and  arranged  for  the  two  ends  of  the  tube 
to  be  open  to  the  portion  of  the  air  current  between  which 
the  difference  of  pressure  is  to  be  measured.  Measurements 
of  the  pressure  between  the  atmosphere  and  any  portion  of  a 
ventilating  air  current  are  made  by  allowing  one  end  of  the 
tube  to  be  open  to  the  atmosphere  and  connecting  the  other 
end  to  the  air  current  whose  pressure  is  to  be  measured. 
Water  gages  are  often  arranged  with  one  end  of  the  tube 
bent  at  right  angles,  the  tube  itself  being  held  upon  a  flat 
board,  very  much  in  the  same  way  as  a  thermometer  is  held, 
and  the  bent  end  of  the  tube  being  pushed  through  a  hole  in 
the  board.  A  length  of  india  rubber  tube  can  be  employed  to 
connect  the  ends  of  the  tube  with  the  atmosphere  to  be 
measured. 

For  measuring  very  small  differences  of  pressure  the  micro- 
manometer  shown  in  Fig.  71  may  be  employed.  It  is  claimed 
that  readings  to  1/2000  millimeter  may  be  obtained. 

ESTIMATING  THE   HEAT  TO  BE  PROVIDED. 

In  the  preceding  sections  the  writer  has  explained  how  the 


ESTIMATING  THE  HEAT  TO  BE  PROVIDED.  255 

heat  is  delivered  from  the  different  appliances  to  the  air  of  the 
room,  how  the  air  entering  a  room  is  heated  and  how  the 
ventilating  current  is  made  use  of  to  heat  and  cool  a  room, 
etc.  In  a  later  section  he  proposes  to  estimate  the  probable 
quantity  of  heating  apparatus  and  the  probable  current  re- 
quired to  heat  a  large  ocean  liner  throughout  by  electricity. 


FIG.    71. — THE    MICROMANOMETER. 

Before  doing  so  it  will  perhaps  be  as  well  to  consider  how  the 
heat  that  is  required  has  to  be  estimated. 

In  the  earlier  articles  it  was  pointed  out  that  the  heating 
apparatus  in  a  great  many  cases  was  left  to  heat  up  the  room, 
the  saloon,  etc.,  as  best  it  could;  and  in  other  cases  the  air 
was  heated  as  it  entered  the  room,  either  by  appliances  in  the 
room  or  by  appliances  placed  in  the  path  of  the  air  current. 
But  he  has  not  dealt  in  detail  with  the  quantity  of  heat  that 


256  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

has  to  be  provided.  The  conditions,  of  course,  will  vary  with 
the  different  climates  a  ship  may  be  passing  through  and  with 
the  different  times  of  the  year,  but  the  same  rules  will  apply 
in  all  cases.  It  is  not  sufficient  to  assume  that  the  air  of  a 
room  is  heated  up  by  the  heating  appliance  and  remains 
heated.  This  is  what  used  to  be  assumed  in  the  old  days  of 
open  fireplaces  and  natural  ventilation. 

The  modern  heating  and  ventilating  engineer  carefully  esti- 
mates the  quantity  of  heat  that  passes  out  of  the  space  to  be 
warmed  in  exactly  the  same  manner  as  he  estimates  the  quan- 
tity of  heat  that  he  can  deliver  to  the  space  through  the  sur- 
faces of  his  heating  appliances.  Evidently  there  will  be  two 
distinct  sources  of  loss  of  heat  in  any  room  to  be  warmed — 
the  entrance  of  cold  air  from  outside  and  the  passage  of  heat, 
from  the  room  to  be  heated,  through  the  walls,  floors,  ceilings, 
etc.  The  first  source  of  loss,  the  entrance  of  cold  air,  is  ex- 
ceedingly difficult  to  estimate  for.  It  is  usual  to  provide 
against  it,  as  far  as  possible,  by  warming  the  corridors,  alley- 
ways, vestibules,  etc.,  and  in  tin  present  case  it  will  be  left 
out  of  the  calculation,  it  being  assumed  that  the  air  of  the 
alleyways,  etc.,  is  warmed  to  a  temperature  of  10  degrees 
above  that  of  the  outside  atmosphere.  The  heat  to  be  provided 
then  consists  of  two  quantities — that  :equired  to  raise  the 
temperature  of  the  air  and  the  objects  in  the  room  to  the 
desired  amount,  and  that  required  to  replace  the  heat  passing 
out  through  the  walls,  floors,  etc. 

THE  HEAT   PASSING   OUT   THROUGH    THE   SHIP'S   SIDE,   BULKHEADS, 

ETC. 

It  will  be  understood  from  what  has  been  said  with  regard 
to  the  passage  of  heat  from  a  higher  temperature  to  a  lower, 
that  the  rule  given  as  to  the  passage  of  heat  from  a  heating 
appliance  to  the  surrounding  air  applies  equally  to  the  pas- 
sage of  heat  from  the  air  in  a  stateroom  to  the  water  outside 


THE  HEAT   PASSING  OUT.  257 

the  ship,  or  to  the  air  on  the  other  side  of  the  bulkheads,  the 
other  sides  of  the  deck,  etc.  That  is  to  say,  the  passage  of 
heat  through  the  ship's  side,  t!:e  bulkheads,  etc.,  will  be  in 
direct  proportion  to  the  difference  of  temperature  between  the 
inside  of  the  stateroom  and  the  water  or  air  on  the  outside  of 
the  ship  or  the  bulkhead,  in  direct  proportion  to  the  surface 
exposed  to  the  action  and  to  the  thermal  conductivity  of  the 
substance  of  which  the  walls  of  the  stateroom  are  composed. 
The  heating  appliance,  whatever  it  is,  must  deliver  heat  to  the 
stateroom  at  the  same  rate  as  it  is  carried  off. 

Assuming  the  temperature  of  the  stateroom  to  be  main- 
tained at  70  degrees  F.,  the  temperature  to  be  worked  to  out- 
side the  walls  of  the  stateroom  is  evidently  the  lowest  that  is 
likely  to  be  met  with  during  the  ship's  voyage,  and  this  will 
vary  with  the  climates  into  which  the  ship  goes  and  with  the 
seasons.  Whalers  and  sealers,  and  ships  which  go  into  the 
very  cold  regions  in  the  neighborhood  of  the  Arctic  circle,  will 
be  subject  to  very  low  temperatures,  while  those  which  are 
engaged  in  the  bulk  of  the  ocean  traffic,  crossing  the  Atlantic 
and  the  Pacific  in  various  directions,  will  not  have  such  wide 
variations.  In  the  calculations  which  follow,  a  minimum 
temperature  of  30  degrees  F.  is  taken  for  the  sea  and  40 
degrees  F.  for  the  air  outside  of  the  staterooms,  with  the 
proviso  that  for  ships  in  which  lower  temperatures  are  met 
with,  these  lower  temperatures  must  be  substituted  in  the 
calculations.  It  is  also  assumed  that  the  air  in  the  alleyways, 
corridors,  and  generally  between  decks,  will  be  warmed  to  a 
temperature  10  degrees  above  that  of  the  outside  atmosphere. 

In  houses  in  Canada  and  America,  that  are  subject  to  very 
low  temperatures  in  winter,  it  is  usual  to  raise  the  temperature 
of  the  halls,  passages,  etc.,  to  very  nearly  that  of  the  living 
rooms,  as  serious  colds  might  be  taken  if  this  were  not  done. 
Also,  in  the  case  of  institutions  in  the  United  Kingdom,  such 
as  hospitals,  hotels,  technical  colleges,  etc.,  that  are  warmed 


258  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

and  ventilated  on  the  plenum  system,  the  temperature  of  the 
corridors,  passages,  etc.,  is  practically  the  same  as  that  of  the 
wards,  coffee  rooms,  class  rooms,  etc. 

Take  a  stateroom  having  a  cubical  capacity  of  1,100  cubic 
feet — this  figure  is  taken  to  simplify  calculations — the  dimen- 
sions being  12  feet  long  (fore  and  aft)  by  nlA  feet  wide  and 
8  feet  high.  The  surface  exposed  to  conduction  from  the  air 
of  the  room  to  the  water  outside  will  be  96  square  feet,  and 
that  exposed  to  the  air,  either  of  other  staterooms  or  of  corri- 
dors, etc.,  will  be  8  X  35  =  289  square  feet.  The  surfaces  of 
the  decks,  above  and  below,  will  be  2  X  138  =  276  square  feet. 

We  may  consider  that  the  96  square  feet  of  the  ship's  side 
is  subject  to  a  difference  of  temperature  of  40  degrees  F.  Iron 
has  a  conductivity,  according  to  Box,  of  23s  British  thermal 
units  per  square  foot  per  hour  per  1  degree  F.  It  will  be  seen, 
if  the  stateroom  is  not  lined  with  wood  on  the  ship's  side, 
how  enormous  will  be  the  transference  of  heat  from  the  air 
of  the  room  through  the  ship's  side  to  the  water.  Under  the 
conditions  given  above  the  quantity  of  heat  passing  out  would 
be  over  half  a  million  units  per  hour,  requiring  a  very  large 
heating  apparatus  to  replace  it.  Incidentally,  this  shows  the 
difficulty  of  warming  parts  of  the  ship  where  the  naked  side 
plates,  etc.,  are  exposed  to  the  water  on  one  side  and  the  air 
of  the  ship  on  the  other  in  very  cold  climates,  and  the  ad- 
vantage of  wooden  ships,  in  this  respect,  in  cold  climates. 

A  study  of  cold-storage  methods  enables  the  problem  to  be 
very  effectively  dealt  with,  and  the  passage  of  heat  from  the 
staterooms,  saloons  or  any  part  of  the  ship  to  be  effectively 
prevented.  A  lining  of  wood  is  in  itself  effective,  because 
wood  has  a  conductivity,  according  to  Box,  in  the  neighbor- 
hood of  0.8  unit  per  hour  for  a  thickness  of  1  inch,  and  if  the 
wood  lining  is  so  arranged  as  to  inclose  a  small  air  space 
between  itself  and  the  ship's  plates,  and  more  particularly  if 
the  aii"  space  is  divided  up  into  small  spaces,  so  that  convection 


HEATING   A   PASSENGER    STEAMER   BY   ELECTRICITY.  259 

air  currents  shall  not  have  much  room  to  circulate,  and  if  the 
wood  lining  is  thoroughly  dry,  the  leakage  of  heat  from  the 
staterooms  or  saloons,  under  these  conditions,  may  easily  be 
reduced  to  0.5  unit  per  hour  per  degree  F.  difference  of  tem- 
perature for  each  square  foot  of  surface  of  the  room  all  over. 

Taking  the  dimensions  given  above,  the  total  surfaces  equal 
652  square  feet,  of  which  96  square  feet  will  be  transmitting 
1,920  units  per  hour,  and  the  remaining  556  square  feet  8,340 
units  per  hour,  making  a  total  of  10,260  units  per  hour,  which 
would  lower  the  temperature  of  a  room  of  the  size  given  9.3 
degrees  F.  per  hour,  unless  it  was  replaced  from  a  heating 
appliance. 

With  electrical  apparatus  this  means  that  3,000  watts  must 
be  delivered  to  the  heating  appliances,  and  this  would  require 
three  of  the  usual  four-lamp  luminous  radiators,  one  non- 
luminous  radiator  of  3,000  watts,  two  of  1,500  watts  each,  or 
any  other  equivalent.  With  hot  water  or  steam,  taking  the 
rate  given  above  of  1.5  heat  units  liberated  per  square  foot  of 
heating  surface  per  degree  F.  difference  of  temperature,  and 
assuming  the  hot-water  apparatus  to  have  a  temperature  of 
170  degrees,  10,260  heat  units  would  require  approximately 
70  square  feet  of  heating  surface.  With  steam  at  210  degrees 
the  heating  surface  would  be  approximately  50  square  feet. 

In  the  estimate  for  heating  an  ocean  liner  entirely  by  elec- 
tricity the  calculations  have  been  made  on  these  lines,  the 
surfaces  through  which  heat  passes  out  being  estimated,  and 
the  quantity  of  heat  calculated  from  the  differences  of  tem- 
perature, etc. 

THE    HEATING   BY    ELECTRICITY    OF    A   LARGE    PASSENGER    STEAMER. 

The  writer  has  outlined  a  scheme  for  heating  a  large  pas- 
senger steamer  throughout  by  electrical  apparatus,  and  he 
has  selected  for  the  purpose  the  North  German  Lloyd  steamer 
Kaiser    Wilhclni   der  Grosse,  which  has   a   displacement  of 


260  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

20,000  tons,  carries  a  crew  of  450,  and  has  accommodation  for 
1,500  passengers — first,  second  and  third  class.  Her  dimensions 
are:  Length,  625  feet;  breadth,  66  feet;  depth,  43  feet.  It 
will  be  understood  that  a  scheme  of  the  kind  can  be  only 
approximate.  As  engineers  know  well,  the  figures  for  each 
case,  in  engineering  practice,  have  to  be  worked  out  by  them- 
selves, and  the  present  writer  has  not  the  whole  of  the  neces- 
sary figures  before  him  to  enable  him  to  make  an  exact  esti- 
mate. The  figures  will,  however,  he  believes,  be  sufficiently 
accurate  to  show  what  can  be  done  by  electrical  heating  appa- 
ratus, and  what  it  is  likely  to  cost.  The  writer  has  also  taken 
into  account  in  the  heating  appliances  only  the  passenger 
accommodation  and  its  accessories. 

The  Kaiser  Wilhelm  der  Grosse  has : 

A  first  class  dining  saloon,  measuring  no  by  65  feet,  placed 
amidships  on  the  main  deck;  a  second  class  dining  saloon, 
measuring  50  by  55  feet,  aft  on  the  main  deck;  a  children's 
saloon,  measuring  44  by  26  feet,  aft  on  the  main  deck ;  a 
children's  dining  saloon,  measuring  45  by  30  feet,  forward  on 
the  main  deck ;  an  auxiliary  second  class  dining  saloon,  50  by 
15  feet,  aft  on  the  upper  deck ;  a  first  class  drawing  room,  32 
by  30  feet,  amidships  on  the  promenade  deck;  a  second  class 
drawing  room,  25  by  20  feet,  aft  on  the  upper  deck ;  a  first 
class  smoke  room,  33  by  40  feet,  forward  on  the  promenade 
deck ;  a  second  class  smoke  room,  38  by  26  feet,  aft  on  the 
promenade  deck ;  a  reading  room,  30  by  20  feet,  forward  on 
the  promenade  deck. 

It  has  also  accommodation  for  third  class  passengers  on  the 
lower  deck  totaling  200  by  34  feet ;  also  for  stewards  for 
third  class  passengers  on  the  lower  deck  totaling  120  by  20 
feet ;  accommodation  for  third  class  passengers  on  the  main 
deck,  42  by  40  feet ;  accommodation  for  attendants  on  the  main 
deck,  40  by  20  feet. 

In  addition  there  are  some  260  spaces  to  be  heated,  comprising 


HEATING   A   PASSENGER   STEAMER   BY    ELECTRICITY.  261 

staterooms,  hospitals,  kitchens,  pantries,  lavatories,  etc.,  and 
there  are  the  usual  vestibules  to  the  saloon,  in  which  the 
stairs  leading  from  one  deck  to  the  other  in  the  passenger 
departments  are  fixed. 

The  height  between  decks  for  the  promenade,  upper  and 
main  decks,  is  8  feet,  and  that  of  the  lower  deck  is  7  feet. 
There  is  the  usual  orlop  deck,  but  it  is  occupied  mainly  by 
boilers,  coal  bunkers,  cargo,  baggage,  chain  lockers,  etc. 

The  writer  has  divided  the  staterooms  and  similar  spaces 
into  two  sizes  to  simplify  the  calculations.  One  lot,  of  which 
he  makes  out  that  there  are  approximately  100,  measure  10  by 
10  feet  by  8  feet  high.  The  smaller  ones,  of  which  there  are 
about  160,  measure  8  by  6  feet  by  8  feet  high. 

In  calculating  the  heating  apparatus  required  and  the  quan- 
tity of  current  to  furnish  the  necessary  heat,  the  writer  has 
worked  to  the  same  figures  as  were  used  in  explaining  how 
to  calculate  the  quantity  of  heat  that  must  be  provided  by  any 
heating  apparatus  to  make  up  for  the  heat  lost  by  passing  out 
through  the  sides  of  the  ship,  the  bulkheads  of  cabins,  saloons, 
etc.,  and  the  decks  above  and  below.  The  problem,  it  will  be 
seen,  is  similar  to  that  which  the  refrigeration  engineer  has  to 
deal  with.  In  the  case  of  cold  storage  the  problem  is  to  carry 
off  the  heat  that  passes  in  through  the  walls,  decks,  etc.,  of  the 
cold  chamber.  In  the  present  case  the  problem  is  to  deliver 
heat  to  the  rooms  to  be  warmed,  to  make  up  for  that  which 
has  passed  out  through  the  walls,  decks,  etc. 

To  estimate  the  quantity  of  heat  that  must  be  delivered  by 
any  heating  appliance,  the  quantity  of  heat  passing  out  of  the 
room  to  be  warmed  must  be  estimated  by  taking  the  surfaces 
through  which  heat  can  escape,  the  quantity  of  heat  escaping 
per  square  foot,  and  the  difference  of  temperature  between 
the  inside  and  the  outside.  The  rate  of  passage  outwards  of 
heat  the  writer  has  taken  at  the  figure  given  in  a  previous 
article,  0.5  British  thermal  unit  per  hour  per  square  foot  per 


262  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

degree  F.  difference  of  temperature  between  the  inside  and 
the  outside ;  with  one  exception,  that  of  the  skylights  of  the 
first  class  dining  saloon  and  the  first  class  drawing  room.  The 
rate  at  which  heat  passes  through  glass  is  very  much  higher 
than  that  at  which  it  passes  through  wood,  and  it  has  been 
assumed,  in  all  the  calculations,  that  wood  is  the  substance 
through  which  the  heat  from  the  saloons,  state  rooms,  etc.,  has 
to  escape,  except  in  the  case  of  the  skylights  mentioned. 

The  writer  has  also  taken  the  figures  mentioned  in  a  pre- 
vious section,  viz. :  a  minimum  temperature  of  30  degrees  F. 
outside  the  ship  and  a  temperature  to  be  maintained  in  the 
rooms  to  be  warmed  of  70  degrees  F.  In  a  great  deal  of 
the  passenger  service  the  minimum  temperature  mentioned, 
30  degrees  F.,  will  not  be  reached.  Probably  a  temperature  of 
40  degrees  F.  would  be  more  like  the  average,  but  even  cross- 
ing the  Atlantic  in  winter  very  much  lower  temperatures  are 
met  with.  The  calculation  is  intended  as  a  guide  only,  and 
must  be  altered  to  suit  the  temperatures,  and  it  is  a  very 
simple  matter  to  do  so.  Thus,  the  extreme  range  of  tem- 
perature taken  in  the  writer's  calculations  is  a  difference  of 
40  degrees  F.  For  ships  which  meet  temperatures  of  20  de- 
grees F.  an  addition  of  25  percent  to  the  heat  required  to  be 
delivered  will  be  necessary,  and  to  the  heat-furnishing  ap- 
pliance. To  ships  meeting  temperatures  of  10  degrees  F.  an 
addition  of  50  percent  to  the  writer's  figures  will  be  required. 
For  the  average  minimum  of  40  degrees  F.,  which  will  prob- 
ably meet  the  case  of  a  large  number  of  ships,  the  writer's 
figures  may  be  reduced  by  25  percent. 

It  should  also  be  noted  that  the  writer  has  taken  70  degrees 
F.  as  his  standard  of  temperature  within  the  rooms  to  be 
warmed,  this  being  the  temperature  to  which  Americans  are 
accustomed.  Europeans  are  accustomed  to  take  standard  tem- 
peratures of  60  degrees,  or  at  most  65  degrees  F.  For  those 
ships  where  a  standard  of  60  degrees  F.  would  be  sufficient 


HEATING   A   PASSENGER   STEAMER   BY    ELECTRICITY.  263 

for  living  places  the  writer's  figures  may  again  be  reduced 
by  25  percent. 

In  drawing  his  estimate,  also,  the  writer  has  assumed  that  the 
heating  appliances  would  be  placed  in  the  best  position  for 
distributing  the  heat  to  the  best  advantage.  On  board  ship 
there  is  not  the  same  trouble  as  on  shore  with  chimneys, 
except  in  those  saloons  that  are  furnished  with  grates,  fires 
and  so  on,  and  therefore  there  is  not  the  danger  of  the  heat 
liberated  by  the  heating  appliance  being  carried  off  up  the 
chimney.  Ventilation,  of  course,  must  be  provided,  and,  as 
already  indicated,  the  best  method  is  to  place  the  heating 
appliance  in  the  path  of  the  ventilating  air  current,  where  it 
enters  the  room  to  be  warmed.  Where  there  is  no  special 
ventilating  arrangement  the  heating  appliances  should  be 
placed  as  far  as  possible  in  the  line  of  the  natural  ventilating 
air  current,  the  air  which  comes  in  under  doors  and  by  other 
openings  as  it  enters  the  room. 

There  are  two  or  three  important  points  that  should  be 
noted  in  connection  with  the  calculations  for  the  size  of  heat- 
ing appliance  required  and  the  quantity  of  current.  Thus,  of 
the  two  sizes  of  staterooms,  the  larger  measuring  10  by  10  feet 
by  8  feet,  or  800  cubic  feet,  and  the  smaller  8  by  6  feet  by  8 
feet,  or  384  cubic  feet,  say  400  cubic  feet  in  round  figures ; 
owing  to  the  much  larger  surface  in  the  10-foot  rooms  above 
that  exposed  in  the  8-foot  rooms,  the  amount  of  heat  passing 
out  through  the  walls,  etc.,  and  the  amount  of  heat  therefore 
required  to  be  delivered  to  the  air  of  the  rooms  to  make  it  up, 
is  enormously  larger  for  the  large  rooms  than  for  the  smaller, 
as  will  be  explained. 

In  the  present  case,  also,  the  first  class  dining  room  anc/ 
drawing  room  are  exceptionally  well  placed,  as  far  as  the 
requirement  of  heating  appliances  is  concerned,  because  they 
lie  between  two  funnels.  The  funnels,  of  course,  are  protected 
on  the  outside,  so  that  the  passage  of  heat  outwards  is  a 


264  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

minimum,  but  the  writer  has  assumed  that  a  certain  quantity 
of  heat  does  pass  from  the  funnel  casing  into  the  dining  and 
drawing  rooms.  It  is  a  case  of  heat  passing  into  these  rooms 
in  place  of  passing  out  of  them,  and  the  quantity  of  heat  that 
has  to  be  delivered  by  any  heating  apparatus  to  these  rooms 
is  lessened  by  the  heat  delivered  from  the  funnels.  In  esti- 
mating the  heat  required  for  the  dining  saloon  the  writer  has 
taken  the  heat  passing  out  through  the  ship's  side,  the  decks 
above  and  below  and  the  skylight,  and  has  subtracted  from  it 
the  heat  he  estimates  will  pass  in  from  the  funnel  casing.  In 
the  case  also  of  the  alleyways,  as  the  engine-room  funnel  and 
stoke-hold  casings  will  line  the  alleyways  for  a  large  portion 
of  the  length  of  the  ship,  and  as  a  considerable  amount  of 
heat  must  pass  from  them  into  the  alleyways,  the  writer  has 
assumed  that  the  temperature  of  the  air  in  the  alleyways  will 
be  raised  10  degrees  above  that  of  the  air  outside  during  cold 
weather. 

APPARATUS    ESTIMATED    TO    BE    REQUIRED    FOR    HEATING    THE    DIF- 
FERENT   SALOONS,    STATE    CABINS,    ETC. 

The  electrical  heating  appliances,  it  was  explained,  are  made 
in  various  sizes  to  absorb  from  200  watts  up  to  6,000  watts. 
These  heating  appliances,  it  will  be  remembered,  are  divided 
into  two  distinct  varieties,  those  in  which  the  long  incandes- 
cent electric  lamps  are  employed  and  those  in  which  non- 
luminous  resistances  are  employed.  The  lamps  are  usually 
arranged  to  absorb  250  watts  each,  though  the  Prometheus 
Company,  of  Great  Britain,  has  recently  introduced  lamps 
taking  350  watts,  and  burning  at  a  red  heat  in  place  of  a  yellow 
heat.  The  250-watt  lamp,  however,  forms  a  very  convenient 
standard,  particularly  as  it  is  made  up  into  appliances  carrying 
2,  3  and  4  lamps,  and  in  the  following  estimate  the  writer  gives 
the  figures  in  watts  required  and  in  lamps  of  250  watts  each : 

The  first  class  dining   saloon  requires  the   expenditure   of 


COST    OF    FURNISHING    THE    HEAT.  265 

4500  watts,  or  18  lamps.  The  first  class  drawing  room  re- 
quires the  expenditure  of  1,400  watts,  or  6  lamps.  The  second 
class  dining  room  requires  3,500  watts,  or  14  lamps.  The 
children's  dining  room  requires  3,000  watts,  or  12  lamps.  The 
children's  saloon  requires  2,500  watts,  or  10  lamps.  The 
auxiliary  second  class  saloon  requires  1,250  watts,  or  5  lamps. 
The  first  class  smoke  room  requires  2,000  watts,  or  8  lamps. 
The  second  class  smoke  room  requires  1,500  watts,  or  6 
lamps.  The  reading  room  requires  the  expenditure  of  1,000 
watts,  or  4  lamps.  The  third  class  passengers'  quarters,  stew- 
ards, attendants,  etc.,  require  6,000  watts,  or  24  lamps. 

The  large  staterooms,  the  writer  makes  out,  require  2,500 
watts,  or  10  lamps,  and  the  smaller  staterooms  250  watts,  or 
even  less,  or  1  lamp.  Taking  the  number  of  the  larger  state- 
rooms at  100,  this  means  1,000  lamps  in  addition,  and  the 
number  of  the  smaller  rooms  at  160  means  160  more  lamps. 
In  addition  to  the  above  there  are  the  vestibules  mentioned. 

The  total  number  of  250-watt  lamps  given  in  the  above  list 
is  1,267,  and  it  will  therefore  be  wise  to  allow  for  a  total,  to 
cover  all  contingencies,  of  1,500  lamps  of  250  watts,  or  for 
a  current  of  375  kilowatts. 

The  above  figures  are  for  the  minimum  outside  temperature 
mentioned,  30  degrees  F.  If  a  temperature  of  20  degrees  F. 
has  to  be  provided  for  1,875  lamps,  or  say  a  current  of  470 
kilowatts,  would  be  required.  With  a  temperature  of  10  de- 
grees F.,  2,250  lamps  and  a  current  of  565  kilowatts  would 
be  required.  With  a  temperature  of  30  degrees  below  zero  F., 
or  100  degrees  F.  difference  between  the  outside  and  the  rooms 
to  be  warmed,  3,750  lamps  would  be  required,  and  a  plant 
capable  of  furnishing  940  kilowatts,  or  about  1,250  horsepower. 

THE    COST    OF    FURNISHING    THE    HEAT    REQUIRED. 

So  far  as  the  writer  has  been  able  to  ascertain,  no  figures 
have  yet  been  accurately  taken  out  giving  the  cost  of  generating 


266  THE    HEATING    AND    VENTILATING    OF    SHIPS. 

current  on  board  ship.  With  electric  lighting  as  an  auxiliary 
the  steam  required  has  gone  in  with  other  auxiliaries.  On 
the  other  hand,  it  is  often  not  the  rule  to  condense  the 
steam  used  by  auxiliaries,  and  the  consumption  of  electric 
light  engines  is  taken  at  about  40  pounds  of  steam  per  kilowatt- 
hour.  But  it  must  be  remembered  that  the  steam  is  being 
generated  under  the  most  economical  conditions.  The  steamer 
crossing  the  Atlantic,  or  at  sea  for  any  number  of  days,  under 
any  possible  conditions,  providing  she  is  continuously  steam- 
ing, is  generating  steam  under  the  most  favorable  conditions 
known  to  the  engineer.  There  are  practically  no  stand-by 
losses,  such  as  send  up  the  fuel  cost  so  much  on  shore. 

On  shore,  it  will  be  remembered,  lighting  is  required  only 
for  a  certain  number  of  hours  during  the  day,  and  power  even 
is  required  only  for  a  certain  number  of  hours,  and  there  are 
portions  of  the  day,  both  with  lighting  and  with  such  power 
services  as  that  for  tramways  and  suburban  railways,  when 
the  quantity  of  current  is  very  high  indeed  for  a  short  time, 
dropping  to  something  very  small  between  those  times.  This 
means  that  either  boiler  furnaces  have  to  be  banked  or  they 
have  to  be  let  out  and  relighted.  In  either  case  it  means  the 
consumption  of  a  considerable  quantity  of  fuel  not  required 
in  steamship  work.  Further,  the  oil  and  petty  stores  and  other 
things  required  for  electrical  generating  plant  on  board  ship, 
are  part  only  of  a  large  whole,  and  therefore  should  be  ob- 
tained more  economically,  providing  proper  care  is  used  in 
issuing  stores,  than  where  the  plant,  often  a  comparatively 
small  one,  has  to  buy  everything  specially  for  its  own  use. 

The  attendance,  also,  in  the  case  of  a  shipboard  electricity 
generating  plant,  should  be  smaller  than  for  a  similar  plant 
on  shore.  Boiler  attendance  goes  in  with  that  of  the  main 
engines.  Even  a  very  large  electricity  generating  plant  will 
not  make  much  appreciable  difference  to  the  stoke-hold  labor 
of  a  ship  of  20,000  tons  and  of  27.000  horsepower,  such  as 
the    Kaiser    Wilhelm    der    Grosse.      Attendance,    in    fact,    is 


COST    OF    FURNISHING    THE   HEAT.  267 

resolved  into  that  of  the  electrician  on  watch,  with  possibly 
an  assistant  to  oil,  and  the  electrician  to  look  after  the  appa- 
ratus in  use,  to  make  good  little  breakages,  keep  switches 
right,  etc. 

The  writer  thinks  that  he  will  not  err  on  the  side  of  optimism 
if  he  takes  the  cost  of  electricity  at  o.5d.  (one  cent)  per 
kilowatt-hour  (Board  of  Trade  unit,  as  it  is  called  on  shore  in 
the  United  Kingdom).  In  America  there  are  many  electrical 
generating  plants,  generating  current  for  railways  and  other 
purposes,  in  which  the  cost  is  very  much  less  than  the  figure 
taken  above,  and  there  are  cases  even  in  the  United  King- 
dom of  electrical  generating  plants  at  collieries  and  in  other 
works  where  the  cost  of  generation  is  much  less  than  o.5d. 
If  the  above  figure  is  taken,  therefore,  any  estimates  founded 
upon  it  should  be  fairly  safe 

The  heating  appliances  detailed  for  the  different  saloons, 
etc.,  total  up  to  107  lamps  of  250  watts  each.  These  heating 
appliances  will  probably  be  required  from  8  A.  M.  to  mid- 
night, or  say  16  hours,  and  in  addition  a  certain  number  of 
the  smaller  staterooms,  and  possibly  a  few  of  the  larger 
ones,  will  probably  be  required  during  the  same  hours,  and 
therefore  it  will  probably  be  approximately  correct  to  assume 
240  lamps  of  250  watts  each  as  being  employed  for  16  hours 
per  day.  This  means  60  kilowatts  for  16  hours,  or  960  kilowatt- 
hours  per  day.  The  writer  estimates  that  probably  60  lamps 
of  250  watts  will  be  required  for  the  full  24  hours;  this 
equals  15  kilowatts  for  24  hours,  or  360  kilowatt-hours.  Of 
the  remainder,  the  staterooms  and  other  places  will  be  re- 
quired for  probably  4  hours  during  the  day.  In  addition  there 
will  be  some  1,200  lamps  of  250  kilowatts,  or  the  equivalent, 
which  will  probably  be  required  for  4  hours  out  of  the  24. 
This  means  300  kilowatts  for  4  hours,  and  equals  1,200 
kilowatt-hours.  Adding  these  together,  the  total  is  2,520 
kilowatt-hours  per  day. 


268  THE    HEATING    AND    VENTILATING    OF     SHIPS. 

This  would  cost,  at  o.5d.  per  kilowatt,  £5.5.0  ($25.55)  per 
day,  or  say  £31.10.0  ($i53-3o)  for  a  six-day  passage  across  the 
Atlantic.  If  20  degrees  F.  is  taken  as  the  minimum  tempera- 
ture the  total  cost  will  be  £39.7.6  ($191.62)  for  the  trip;  if  10 
degrees  F.  is  the  minimum,  £47.5.0  ($229.95),  and  for  lower 
figures  in  proportion.  For  ships  trading  to  very  cold  climates, 
and  where  economy  is  essential,  where  also  the  heating  would 
be  required  for  months  together,  the  cost  would  probably  be 
prohibitive  in  the  great  majority  of  ships.  With  a  temperature 
of  —  30  degrees  F.,  or  100  degrees  F.  difference,  the  cost  of 
heating  would  be  £13.2.6.  ($63.88)  per  day  for  a  ship  of  the 
size  of  the  Kaiser  Wilhelm  der  Grosse,  and  with  its  crew  and 
passengers.  But  as  ships  which  go  on  whaling  cruises  do  not 
carry  passengers  nor  large  crews,  electric  heating  even  then 
might  be  found  economical,  on  account  of  its  convenience,  in 
some  cases. 

The  heating  can  be  carried  out  at  less  cost  by  the  steam  or 
hot  water  appliances  that  have  been  named,  but  as  in  so  many 
other  things  the  great  convenience  of  the  electrical  method  of 
distribution  and  of  control  more  than  counterbalances  the  in- 
creased cost,  which,  as  will  be  seen,  is  but  a  very  trifling  sum, 
as  against  the  whole  cost  of  running  a  steamship  of  the  size  of 
the  Kaiser  Wilhelm  der  Grosse  across  the  Atlantic.  There 
are,  of  course,  other  points  to  be  considered.  Additional  plant 
will  be  required  to  furnish  the  current,  and  it  would  probably 
not  be  safe  to  have  less  than  500  kilowatts  for  the  special 
heating  appliances  in  the  case  of  the  ship  considered,  and  under 
the  conditions  named,  and  larger  plant  in  proportion  for  the 
lower  temperatures. 

There  is  the  question  of  finding  room  for  a  500-kilowatt 
plant  and  the  larger  plant  where  required,  though  with  turbo- 
generators this  question  is  reduced  to  a  minimuum.  There  is 
also  the  question  of  the  additional  cables.  Already  the  cable 
problem  is  a  somewhat  serious  one  in  connection  with  lighting. 


COST    OF    FURNISHING    THE    HEAT.  269 

and  the  addition  to  it  of  the  requirements  for  heating  will 
increase  the  trouble.  There  is  no  reason,  however,  that  the 
heating  current  should  not  be  taken  off  the  lighting  service, 
and,  providing  the  conductors  for  the  lighting  service  are 
properly  divided  up,  as  they  always  are  in  modern  steamships, 
so  that  it  is  hardly  possible  for  all  the  lights  to  be  out  at  once, 
the  trouble  of  the  increased  size  of  the  conductor  will  not  be  so 
great.  When  a  cable  reaches  a  certain  size  a  comparatively 
small  addition  in  diameter  gives  it  a  considerably  increased 
conducting  power. 

For  the  lower  temperatures  the  cable  question  would  be 
more  serious.  Everything,  first  cost  and  running  cost,  in- 
creases as  lower  and  lower  temperatures  have  to  be  provided 
for;  but,  again,  in  the  case  of  the  whaler,  as  the  whole  plant 
would  be  small,  the  matter  need  not  be  very  serious. 


A    LIST   OF    BOOKS 


—ON— 


Refrigeration  and   Ice-Making. 


Anderson,  J.  W. — Refrigeration.  An  elementary  text- 
book. Illustrated.  8vo.,  cloth,  242  pp.  New 
York,  1908 Net,  $2.25 

Cooper,  M.—  Practical  Cold  Storage.  The  theory,  de- 
sign and  construction  of  buildings  and  apparatus 
for  the  preservation  of  perishable  products,  ap- 
proved methods  of  applying  refrigeration  and  the 
care  and  handling  of  eggs,  fruit,  dairy  products,  etc. 
Illustrated.  8vo.,  cloth,  572  pp.  Chicago,  1905.  .Net,     3.00 

Goosman,  J.  C. — Carbonic  Acid  Industry.  A  compre- 
hensive review  of  the  manufacture  and  uses  of  C02 ; 
the  commercial  production  of  carbon  dioxide;  de- 
sign and  construction  of  apparatus  and  machinery ; 
efficiency  for  refrigerating  purposes,  etc.  Illus- 
trated.    8vo.,  cloth,  375  pp.     Chicago,  1906.. Net,     2.50 

Gueth,  O. — The  Refrigerating  Engineer's  Pocket  Manual. 
An  indispensable  companion  for  every  engineer  and 
student  interested  in  mechanical  refrigeration.  Illus- 
trated.   i2mo.,  cloth,  155  pp.  New  York,  1908.  .Net,     1.50 

Harding,  R. — The  Ice  and  Refrigeration  Telegraph  Code. 
A  telegraph  code  prepared  expressly  for  manufac- 
turers and  users  of  ice  and  refrigerating  machinery. 
1 2mo.,  flexible  morocco.     Chicago,  1906 Net,     7.50 


Hausbrand,  E. — Evaporating,  Condensing  and  Cooling 
Apparatus;  Explanations,  Formulae  and  Tables  for 
Use  in  Practice.  Translated  from  the  Second  Re- 
vised German  Edition  by  A.  C.  Wright.  Illus- 
trated. 8vo.,  cloth,  400  pp.  New  York  and  Lon- 
don, 1904 Net,  $5.00 

Leask,  A.  Ritchie. — Refrigerating  Machinery.  Its  Prin- 
ciples and  Management.  Fourth  Edition.  Illus- 
trated.    i6mo.,  cloth,  296  pp.     London,  1907 2.00 

Ledoux,  M. — Ice-Making  Machines:  The  theory  of  the 
action  of  the  various  forms  of  cold-producing,  or  so- 
called  Ice  Machines.  Translated,  revised  and  trans- 
formed into  English  units  by  J.  E.  Denton,  D.  S. 
Jacobus  and  A.  Reisenberger.  Sixth  Edition,  Re- 
vised. Illustrated.  i6mo.,  cloth,  190  pp.  New 
York,  1906 5° 

Levey,  J. — Refrigerating  Memoranda;  a  collection  of 
useful  information  relating  to  Ice-Making  and  Re- 
frigerating, gathered  from  engine-room  practice. 
Fifth  Edition.  Illustrated.  321110.,  limp  leather, 
120  pp.     Chicago,  1906 Net,       .75 

Lorenz,  H. — Modern  Refrigerating  Machinery ;'  Its  Con- 
struction, Methods  of  Working  and  Industrial  Appli- 
cations. A  guide  for  engineers  and  owners  of  refrig- 
erating plants.  Authorized  Translation  from  the 
Third  German  Edition  by  Thos.  H.  Pope,  with  chap- 
ters on  American  Practice  in  Refrigeration,  Insula- 
tion, Auditorium  and  Other  Cooling,  by  H.  M. 
Haven  and  F.  W.  Dean.  Illustrated.  8vo., 
cloth,  396  pp.     New  York,  1905 Net,     4.00 

Paulding,  C.  P. — Practical  Laws  and  Data  on  the  Con- 
densation of  Steam  in  Covered  and  Bare  Pipes;  to 
which  is  added  a  translation  of  Peclet's  "Theory 
and  Experiments  on  the  Transmission  of  Heat 
through  Insulating  Materials."  Illustrated.  8vo., 
cloth,  102  pp.     New  York,  1904 Net,     2.00 

Transmission  of  Heat  through  Cold-Storage  Insu- 
lation: Formulas,  Principles  and  Data  relating  to 
insulation  of  every  kind.  A  manual  for  refrigerating 
engineers.  Illustrated,  nmo.,  cloth,  41  pp.  New 
York,  1905 Net,     1.00 


Redwood,  I.  I. — Theoretical  and  Practical  Ammonia  Re- 
frigeration. A  practical  handbook  for  the  use  of 
those  in  charge  of  refrigerating  plants  Fifth  Thou- 
sand. Illustrated.  i6mo.,  cloth,  154  pp.  New 
York,  1904 $1.00 

Schmidt,  L.  M. — Principles  and  Practice  of  Artificial  Ice- 
Making  and  Refrigerating.  Comprising  principles 
and  general  consideration — practice  as  shown  by- 
particular  systems  and  apparatus — insulation  of 
cold-storage  and  ice-houses,  refrigerators,  etc.  Use- 
ful information  and  tables.  Third  Edition,  Revised 
and  Enlarged.  Illustrated.  8vo.,  cloth,  437  pp. 
Philadelphia,  1907 3.00 

Selfc,  N. — Machinery  for  Refrigeration :  being  sundry  ob- 
servations with  regard  to  the  principal  appliances 
employed  in  ice-making  and  refrigeration,  and  upon 
the  laws  relating  to  the  expansion  and  compression 
of  gases,  principally  from  an  Australian  stand- 
point. Illustrated.  8vo.,  cloth,  372  pp.  Chicago, 
1900 3-50 

Siebel,  J.  E. — Compend  of  Mechanical  Refrigeration.  A 
comprehensive  digest  of  General  Engineering  and 
Thermodynamics  for  the  Practical  Use  of  Ice-Manu- 
facturers, Cold-Storage  Men,  Contractors,  Engineers, 
Brewers,  Packers,  and  others  interested  in  the 
Application  of  Refrigeration.  Seventh  Edition. 
Illustrated.  121110.,  cloth,  572  pp.  Chicago, 
1906 Net,     3.50 

Stephansky,  P.  C.  O — The  Practical  Running  of  an  Ice 
and  Refrigerating  Plant.  Illustrated.  i6mo.,  cloth, 
105  pp.     Boston,  1897 2.00 

Voorhees,  G.  T.  —  Indicating  the  Refrigerating  Ma- 
chine :  The  application  of  the  indicator  to  the  am- 
monia compressor  and  steam  engine,  with  practical 
instructions  relating  to  the  construction  and  use  of 
the  indicator  and  reading  and  computing  indicator 
cards.  Illustrated  with  full-page  cuts,  diagrams 
and  tables.  i2mo.,  cloth,  179  pp.  Chicago, 
1899 Net,     1.00 


Wallis-Tayler,    A.     J Refrigeration,    Cold     Storage, 

and  Ice-Making.  A  practical  treatise  on  the  art 
and  science  of  refrigeration.  With  361  cuts  and 
diagrams.  8vo.,  cloth,  610  pp.  London  and  New 
York,  1902 Net,  $4.50 

Refrigerating    and    Ice-Making    Machinery.      A 

descriptive  treatise  for  the  use  of  persons  employing 
refrigerating  and  ice-making  installations  and  others. 
Third  Edition.  Illustrated.  i2mo.,  cloth,  280  pp. 
London  and  New  York,  1902 3.00 

The    Pocket    Book   of    Refrigeration    and    Ice- 


Making.     Fifth  Edition,   Enlarged.     With   31    dia-    "* 
grams  and  numerous  tables.     i6mo.,  cloth,  184  pp. 
New  York,  1907 1.5 

Wilder,  F.  W. — The  Modern  Packing  House.  A  com- 
plete treatise  on  the  designing,  construction,  equip- 
ment and  operation  of  a  modern  abattoir  and  pack- 
ing-house, according  to  present  American  practice. 
Illustrated.    8vo.,  cloth,  581  pp.    Chicago,  1905.  Net,   10.00 

Wood,  De  V. — Thermodynamics,  Heat-Motors,  and  Re- 
frigerating Machines.  Eighth  Edition,  Revised  and 
Enlarged.  Illustrated.  8vo.,  cloth,  486  pp.  New 
York,  1905 4.00 

Williams,  H. — Mechanical  Refrigeration.  Being  a  Prac- 
tical Introduction  to  the  Study  of  Cold  Storage,  Ice- 
Making  and  Other  Purposes  to  which  Refrigeration 
is  being  applied.  Illustrated.  121110.,  cloth,  406 
pp.     New  York,  1903 Net,    2.25 

Any  book  in  this  list  will  be  sent  prepaid  anywhere  in  the  world 
on  receipt  of  price,  by 

D.  Van  Nostrand  Company, 
publishers  anfc  Booksellers, 

23  Murray  and  27  Warren  Sts.,  NEW  YORK. 


02. 


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